Recent advances in research on cowpea diseases. - IITA

Cowpea <strong>in</strong>tegrated pest management2.2<strong>Recent</strong> <strong>advances</strong> <strong>in</strong> <strong>research</strong> on cowpeadiseasesA.M. Emechebe 1 and S.T.O. Lagoke 2AbstractCowpea diseases <strong>in</strong>duced by various pathogenic groups (fungi, bacteria, viruses,nematodes, and parasitic flower<strong>in</strong>g plants) constitute one of the most importantconstra<strong>in</strong>ts to cowpea production <strong>in</strong> all agroecological zones where the crop isgrown. This paper presents an overview of the major <strong>research</strong> f<strong>in</strong>d<strong>in</strong>gs on cowpeadiseases s<strong>in</strong>ce the 1995 World Cowpea Conference. The focal po<strong>in</strong>ts <strong>in</strong>clude considerationof the present state of scientific knowledge of these diseases with specialemphasis on new <strong>in</strong>formation on etiology, biology, distribution, epidemiology,economic significance, and <strong>in</strong>tegrated disease management options. Knowledgegaps that should be bridged through <strong>research</strong> to m<strong>in</strong>imize losses from these diseasesare highlighted wherever necessary.IntroductionCowpea diseases <strong>in</strong>duced by species of pathogens belong<strong>in</strong>g to various pathogenic groups(fungi, bacteria, viruses, nematodes, and parasitic flower<strong>in</strong>g plants) constitute one of themost important constra<strong>in</strong>ts to profitable cowpea production <strong>in</strong> all agroecological zoneswhere the crop is cultivated. At the September 1995 Second World Cowpea Conference,our knowledge about diseases from 1984 (when the first World Cowpea Conference washeld) to 1995 was updated by lead papers on shoot and pod diseases (Emechebe and Flor<strong>in</strong>i1997), parasitic plants (Lane et al. 1997; S<strong>in</strong>gh and Emechebe 1997), nematodes and othersoilborne diseases (Flor<strong>in</strong>i 1997; Roberts et al. 1997), and viruses (Hampton et al. 1997;Huguenot et al. 1997). This paper presents an overview of the major <strong>research</strong> f<strong>in</strong>d<strong>in</strong>gs oncowpea diseases (<strong>in</strong>duced by all the different pathogenic groups) s<strong>in</strong>ce 1995; it highlights<strong>in</strong>formation on new disease records and, wherever possible, updates <strong>in</strong>formation on themajor pathogens, pay<strong>in</strong>g special attention to their biology, distribution, epidemiology,economic significance, and <strong>in</strong>tegrated management options.Distribution of <strong>research</strong> publications among geographical regions, pathogengroups, and themes dur<strong>in</strong>g the past five yearsTo prepare this paper, we reviewed over 340 scientific papers on cowpea diseases publisheddur<strong>in</strong>g the last five years. We have classified these papers to obta<strong>in</strong> the relative contributionsfrom the ma<strong>in</strong> geographical regions––Africa, Asia, Australia, Europe, South Americaand the Caribbean, and North America––as well as their relative distribution among the1. Plant Health Management Division, International Institute of Tropical Agriculture (IITA), KanoStation, PMB 3112, Kano, Nigeria.2. University of Agriculture, Abeokuta, Nigeria.94

<strong>Recent</strong> <strong>advances</strong> <strong>in</strong> <strong>research</strong> on cowpea diseasespr<strong>in</strong>cipal themes (biology, control, economic importance, etiology, epidemiology, systems,and techniques/methodology) and pathogen groups.About 25% and 36% of the publications were contributed by scientists located <strong>in</strong> Africaand Asia, respectively, while those based <strong>in</strong> North America and <strong>in</strong> South America producedalmost 30% (Table 1). Table 2 shows that among the pathogen groups, the fungi attractedabout 36% of the publications, viruses 33%, and nematodes 20% and only about 6% eachof the papers were devoted to bacteria and parasitic flower<strong>in</strong>g plants. It is encourag<strong>in</strong>gthat about 42% of the papers dwelt on the control of the diseases, with about 50% of thesepapers be<strong>in</strong>g on host-plant resistance (Table 3). Of the rema<strong>in</strong><strong>in</strong>g 50% of the publicationson disease control, three ecologically susta<strong>in</strong>able options (biological, cultural, andbotanical) attracted about 34% and pesticides about 17%. This is considered a fair balance.Similarly, the relative number of publications on other <strong>research</strong> themes (especiallyepidemiology, physiology, and techniques) appears to be satisfactory; it is expected that<strong>in</strong> future the effort presently devoted to etiology and surveys will be channeled to theseareas. In the follow<strong>in</strong>g sections, only publications that provide new <strong>in</strong>formation or thatclarify hitherto exist<strong>in</strong>g controversies are reviewed.Table 1. Relative contributions by geographical area to scientific publications on cowpeadiseases (1995–2000).Number of papers Percentage of papersGeographical area contributed contributedAfrica 85 24.8Asia 12.3 35.9Australia 5 1.4Europe 28 8.2South America and Caribbean 27 7.9North America 75 21.8Total 343 100.0Table 2. Publications on cowpea diseases accord<strong>in</strong>g to pathogen groups.Group of pathogens Number of papers Percentage of papersBacteria 21 6.1Fungi 122 35.6Nematodes 69 20.1Parasitic plants 19 5.5Viruses 112 32.7Total 343 100.095

Cowpea <strong>in</strong>tegrated pest managementTable 3. Publications on cowpea diseases grouped accord<strong>in</strong>g to themes.Theme Number of papers Percentage of papersBiology 40 11.3Control: 147 41.7Biocontrol (17) (4.8)Botanicals (11) (3.1)Cultural (22) (6.1)HPR (72) (20.40)Pesticidal (26) (7.30)Cropp<strong>in</strong>g systems 7 2.0Distribution 33 9.3Epidemiology 34 9.6Etiology 38 10.8Mycotox<strong>in</strong>s 1 0.3Physiology 33 9.3Techniques 20 5.7Total 352 100.0Bacterial diseasesThe controversy about the etiology of bacterial blight and bacterial pustule appears tohave persisted after 1995 despite the suggestion by Emechebe and Flor<strong>in</strong>i (1997) thatthe pustule pathogen be regarded as a stra<strong>in</strong> of Xanthomonas campestris pv. vignicola(Burkholder) Dye and not a dist<strong>in</strong>ct pathovar of X. campestris, namely X. campestris pv.vigna unguiculata Patel and J<strong>in</strong>dal as proposed by Patel and J<strong>in</strong>dal (1982). However, <strong>in</strong> arelated publication, Allen et al. (1998) stated categorically that cowpea blight is <strong>in</strong>ducedby X. campestris pv. vignicola while bacterial pustule is <strong>in</strong>duced by X. campestris pv.vigna unguiculata, not a stra<strong>in</strong> of pv. vignicola from which it is dist<strong>in</strong>ct <strong>in</strong> pathogenicity,the s<strong>in</strong>gle feature for def<strong>in</strong>ition of pathovars. To clarify the situation, Khatri-Chhetri et al.(1998a) studied 55 stra<strong>in</strong>s of the bacterium (36 from blight lesions, 13 from pustules, andsix reference stra<strong>in</strong>s) for their metaboliz<strong>in</strong>g pattern of 95 carbon sources us<strong>in</strong>g the BiologGM Microplate System. They reported considerable variation <strong>in</strong> metabolic f<strong>in</strong>gerpr<strong>in</strong>ts ofthe stra<strong>in</strong>s, which were generally correlated with their orig<strong>in</strong> and identification, but not withblight or pustule development and pathogenicity. They concluded that the stra<strong>in</strong>s isolatedfrom blight and pustules from West Africa belonged to the same pathovar, vignicola. In asubsequent study, Verdier et al. (1998) analyzed isolates from cowpea leaves with blightor pustule lesions (collected from 11 countries <strong>in</strong> various geographical areas) and selectedon the basis of pathological and physiological characteristics. The stra<strong>in</strong>s were analyzedfor genotype markers by ribotyp<strong>in</strong>g and by RFLP analysis with a plasmid probe, pth B,conta<strong>in</strong><strong>in</strong>g a gene required for pathogenicity from X. campestris pv. manihotis. Based onpolymorphism detected by pth B among X. campestris pv. vignicola stra<strong>in</strong>s, n<strong>in</strong>e haplotypeswere def<strong>in</strong>ed. However, the genetic variation was <strong>in</strong>dependent of geographic orig<strong>in</strong> ofthe stra<strong>in</strong>s and of pathogenic variation. Based on these results and those of an earlier studyon pathogenic and biochemical characterizations (Khatri-Chhetri et al. 1998b), Verdier etal. (1998) concluded that the stra<strong>in</strong>s isolated from leaves with blight symptoms or m<strong>in</strong>utepustules belonged to the same pathovar, vignicola. This implies that bacterial pustule andblight are <strong>in</strong>duced by different stra<strong>in</strong>s of the same bacterial species.96

<strong>Recent</strong> <strong>advances</strong> <strong>in</strong> <strong>research</strong> on cowpea diseasesThere have been doubts about the taxonomy of the genus Xanthomonas that presentlyhas more than 140 pathovars (Bradbury 1986). To sort out the relationship between themany pathovars and species, a series of studies on the taxonomy of the genus has beenundertaken dur<strong>in</strong>g the last decade to address the species del<strong>in</strong>eation with<strong>in</strong> the genus(Vauter<strong>in</strong> et al. 2000). These studies used analytical f<strong>in</strong>gerpr<strong>in</strong>t<strong>in</strong>g techniques such aselectrophoresis of whole-cell prote<strong>in</strong>s and gas-chromatographic analysis of cellular fattyacids. Results showed that X. campestris pathovars are phenotypically much more diversethan previously documented. The DNA homology matrix dist<strong>in</strong>guished 20 genomic groupswith<strong>in</strong> the genus Xanthomonas (Vauter<strong>in</strong> et al. 1995). Of these, four groups correspondedto four exist<strong>in</strong>g species of Xanthomonas, while 16 DNA homology groups were new andnot consistent with the exist<strong>in</strong>g pathovar classification; these latter 16 genomic groupswere then described as new species (Vauter<strong>in</strong> et al. 1995). As a result of the complexarrangements result<strong>in</strong>g from the DNA homology relationships with<strong>in</strong> the genus, the bacterialblight/pustule pathogen has been placed <strong>in</strong> the species X. axonopodis and is currentlydesignated as X. axonopodis pv. vignicola (Vauter<strong>in</strong> et al. 1995, 2000). This nomenclaturehas received <strong>in</strong>ternational recognition as evidenced by the fact that authorities <strong>in</strong> CABInternational have s<strong>in</strong>ce 1996, consistently <strong>in</strong>cluded the new name <strong>in</strong> square parenthesisafter the former name (X. campestris pv. vignicola) <strong>in</strong> report<strong>in</strong>g abstracts of authors thathad not conformed to the new specific name <strong>in</strong> their monthly publication Review of PlantPathology.Other areas of cowpea bacterial disease <strong>research</strong> that received noteworthy attention<strong>in</strong> the past five years were pathogen survival, field <strong>in</strong>oculation and screen<strong>in</strong>g techniques,and disease control by seed treatment. A study at M<strong>in</strong>jibir, Kano (Nigeria) showed thatplant<strong>in</strong>g spreader l<strong>in</strong>es two weeks before the test l<strong>in</strong>es compared to simultaneous plant<strong>in</strong>gof spreader and test l<strong>in</strong>es <strong>in</strong>creased disease pressure and screen<strong>in</strong>g efficiency (Amusa andOkechukwu 1998). Us<strong>in</strong>g this method, only n<strong>in</strong>e of 45 l<strong>in</strong>es previously rated resistant(follow<strong>in</strong>g simultaneous plant<strong>in</strong>g of spreader and test l<strong>in</strong>es) were confirmed to be resistant.Related studies <strong>in</strong> India have shown that plants spray-<strong>in</strong>oculated at 10–100 days ofage were most susceptible to <strong>in</strong>fection at one month of age (Rakesh et al. 1995). It wasalso shown that the highest <strong>in</strong>fection occurred when plants were spray-<strong>in</strong>oculated twiceat 24-hour <strong>in</strong>tervals under humid conditions. Earlier, Rakesh et al. (1994a) had found thatmaximum disease <strong>in</strong>cidence was obta<strong>in</strong>ed by a spray <strong>in</strong>oculum concentration of 8.6 × 10 8c.f.u./ml, with disease symptoms appear<strong>in</strong>g five days after <strong>in</strong>oculation.Survival studies were conducted <strong>in</strong> Ben<strong>in</strong> Republic and India. In Ben<strong>in</strong>, Sikirou etal. (1998a, b) reported that X. campestris pv. vignicola <strong>in</strong> <strong>in</strong>fected tissue did not survivemore than two months on the soil surface or when buried <strong>in</strong> the soil at a depth of10–20 cm <strong>in</strong> the field. They also reported that out of 12 legume species leaf-<strong>in</strong>filtratedwith X. campestris pv. vignocola, only Sphenostylis stenocarpa (African yam bean)exhibited clear symptoms of bacterial blight. The results of survival studies done <strong>in</strong>India contradict those of Sikirou (1998a, b). A study of the survival of the bacterium<strong>in</strong> <strong>in</strong>fected seed and trash revealed that the bacterium rema<strong>in</strong>ed viable <strong>in</strong> <strong>in</strong>fected seedfor 390 days at 5–10 ºC and 250 days at 10–40 ºC (Rakesh et al. 1994b). In the soil,they showed that X. campestris pv. vignicola survived for 260 days at 10 ºC and 100days at 40 ºC.Good progress towards the control of bacterial blight by seed treatment was reporteddur<strong>in</strong>g the last five years. In India, Thammaiah and Khan (1995a) found that chemical97

Cowpea <strong>in</strong>tegrated pest managementseed treatment with copper oxychloride for 15–60 m<strong>in</strong> completely suppressed seed-transmittedbacterial blight, as did treatment with root or leaf extract of Adhatoda zeylanica for60 m<strong>in</strong> (Thammaiah et al. 1995). Hot water treatment of <strong>in</strong>fected seeds at 52 ºC for 15 m<strong>in</strong>was also effective (Thammaiah and Khan 1995b), higher temperatures be<strong>in</strong>g detrimentalto seed germ<strong>in</strong>ation. By contrast, Sikirou (1999) <strong>in</strong> Ben<strong>in</strong> has reported that seed treatment<strong>in</strong> hot water at 60 ºC for 30 m<strong>in</strong> or 70 ºC for 10 m<strong>in</strong>, or treatment <strong>in</strong> hot air (65 ºCfor 120–144 hr or 70 ºC for 96 hr) elim<strong>in</strong>ated the bacterium from <strong>in</strong>fected seeds without<strong>in</strong>hibit<strong>in</strong>g seed germ<strong>in</strong>ation. The same <strong>research</strong>er has found that <strong>in</strong> cowpea grown <strong>in</strong>alternate rows with maize, the disease severity and <strong>in</strong>cidence were reduced by up to 43%and 41%, respectively while alternate rows of cassava reduced disease severity by up to42% and disease <strong>in</strong>cidence by 34% (Sikirou 1999). There was only one report on yieldloss caused by bacterial blight dur<strong>in</strong>g the period––64% gra<strong>in</strong> yield loss was reported <strong>in</strong>Ben<strong>in</strong> by Sikirou (1999) <strong>in</strong> one of her several field experiments.An important <strong>research</strong> contribution dur<strong>in</strong>g the period under review was the developmentof a semiselective medium (SSM) for easy isolation of the cowpea bacterial blightpathogen. To accomplish this, Khatri-Chhetri et al. (1998b) evaluated 12 carbon and fivenitrogen sources for selectivity towards X. axonopodis pv. vignicola while 25 antibioticswere screened for <strong>in</strong>hibitory effects on saprophytic contam<strong>in</strong>ants frequently isolated fromcowpea leaves (e.g., Pseudomonas fl uorescens, Erw<strong>in</strong>ia herbicola, and Bacillus subtilis).They have designated SSM as cefazol<strong>in</strong>e-cellobiose-methion<strong>in</strong>e medium (CCMM),def<strong>in</strong>ed its composition and the characteristic appearance of the colonies of X. axonopodispv. vignicola, and how the latter can be dist<strong>in</strong>guished from saprophytes not completely<strong>in</strong>hibited by the CCMM.Fungal diseasesNew records of fungal diseases and racesDur<strong>in</strong>g the last five years there have been reports of new records of localized occurrenceseither of well-known diseases or races <strong>in</strong> new areas, or of diseases that had not beenreported before on cowpea. These are described below.Alternaria leaf spot <strong>in</strong> South AfricaGrange and Avel<strong>in</strong>g (1998) have shown that the pathogen of what they considered adestructive foliar disease of cowpea <strong>in</strong> South Africa is Alternaria cassiae Juriar and Khan.The disease occurs also <strong>in</strong> Botswana. The identification of the pathogen to a specific levelmakes it the first report of the species <strong>in</strong> cowpea. However, Emechebe and Flor<strong>in</strong>i (1997)listed leaf spot <strong>in</strong>duced by Alternaria sp. as one of the m<strong>in</strong>or diseases of cowpea, not<strong>in</strong>g itsoccurrence <strong>in</strong> Zimbabwe accord<strong>in</strong>g to Maramba (1983) and Mar<strong>in</strong>ga et al. (1985). Foliarsymptoms, beg<strong>in</strong>n<strong>in</strong>g as semicircular water-soaked lesions at the leaf marg<strong>in</strong>, enlargetowards the center of the leaf and become necrotic. Sporulation occurs at the lower leafsurface as a black velvety mass.Choanephora pod rot <strong>in</strong> ColombiaThis widely distributed pod rot <strong>in</strong>duced by Choanephora cucurbitarum (Berk, and Rav.)Thaxt was reported for the first time <strong>in</strong> the prov<strong>in</strong>ce of Cordoba, Colombia (Munoz andTamayo 1994).98

<strong>Recent</strong> <strong>advances</strong> <strong>in</strong> <strong>research</strong> on cowpea diseasesColletotrichum stem disease <strong>in</strong> South AfricaThis was reported as a new disease <strong>in</strong> South Africa (Smith et al. 1999a). This is probablythe first record of the fungus (C. dematium) <strong>in</strong> cowpea; cowpea was not given as one ofits hosts <strong>in</strong> the comprehensive list by Allen and Lenne (1998). The stem lesions are lightbrown and appear about 48 hours after <strong>in</strong>oculation (Smith et al. 1999a).Latent anthracnoseA latent anthracnose <strong>in</strong> cowpea leaves was reported recently by Latunde-Dada et al.(1999) who have provided details of the <strong>in</strong>fection process. Anthracnose lesions appear onsenescent leaves after a prolonged symptomless period of host colonization last<strong>in</strong>g morethan two weeks. The disease is of no economic importance.Phomopsis pod spot <strong>in</strong> the USAA pod spot disease of cowpea <strong>in</strong> the State of Mississippi (USA) was observed <strong>in</strong> 1994and later shown to be <strong>in</strong>duced by Phomopsis longicola (Roy and Ratnayake 1997). Thedisease, probably a new record on cowpea, appears on mature pods as scattered, irregularblack spots. The fungus is seedborne and also <strong>in</strong>fects soybean.Pre- and postemergence damp<strong>in</strong>g-off <strong>in</strong>duced by Pythium ultimum <strong>in</strong> SouthAfricaThis was a major problem <strong>in</strong> smallholder rural farms under wet soil conditions, caus<strong>in</strong>gseed rot as well as pre- and postemergence damp<strong>in</strong>g-off (Avel<strong>in</strong>g and Adandonon 2000).Germ<strong>in</strong>ated seedl<strong>in</strong>gs fail<strong>in</strong>g to emerge above the soil level were characterized by watersoakedlesions that girdled the hypocotyl. Emerged seedl<strong>in</strong>gs had necrotic taproots andfew lateral roots. Infected hypocotyls above soil level had light brown lesions while someseedl<strong>in</strong>gs showed symptoms of wilt<strong>in</strong>g.A new race of Fusarium oxysporum f.sp. tracheiphilum <strong>in</strong> California, USARace 4 of the cowpea Fusarium wilt fungus (F. oxysporum f. sp. tracheiphilum) hasappeared <strong>in</strong> California (USA) and has been designated as Fot Race 4, which has causedsevere wilt<strong>in</strong>g <strong>in</strong> cultivars CB46 and CB88, known for their resistance to races 1, 2, and3 (Smith et al. 1999b).Macrophom<strong>in</strong>a blightAmong the fungal diseases, Macrophom<strong>in</strong>a blight (Macrophom<strong>in</strong>a phaseol<strong>in</strong>a) hasreceived relatively high <strong>research</strong> attention from workers <strong>in</strong> Africa and Asia because it hasrema<strong>in</strong>ed a serious constra<strong>in</strong>t to cowpea production <strong>in</strong> the drier savannas and the Sahel, thepr<strong>in</strong>cipal zones for cowpea production. Apart from hav<strong>in</strong>g a wide host range, the fungusproduces sclerotia that rema<strong>in</strong> viable <strong>in</strong> the soil for many years and it has been difficultto f<strong>in</strong>d suitable sources of resistance genes among cowpea genotypes. Consequently mostof the effort has been directed towards develop<strong>in</strong>g susta<strong>in</strong>able control options and to abetter understand<strong>in</strong>g of the role of soil environment on pathogenesis.Temperature, be<strong>in</strong>g an important environmental factor, was recently studied by Ratnooet al. (1997), <strong>in</strong> pot experiments <strong>in</strong> India. Their results <strong>in</strong>dicated that Macrophom<strong>in</strong>ablight is favored by high temperatures. Thus, of the four temperature regimes <strong>in</strong>vestigated,highest disease <strong>in</strong>dices were obta<strong>in</strong>ed at 25–40 ºC and 20–35 ºC (disease <strong>in</strong>dicesbe<strong>in</strong>g 100% and 94.5%, respectively) compared to 10–25 ºC and 15–30 ºC. Ratnoo etal. (1997) also found that disease development was low <strong>in</strong> flooded soil compared todrier soil. A similar and more recent study was conducted <strong>in</strong> Niger by Afouda (1999).99

Cowpea <strong>in</strong>tegrated pest managementHe showed that optimum temperature for growth for all eight isolates of M. phaseol<strong>in</strong>awas 30–35 °C, with no growth occurr<strong>in</strong>g at below 13 °C or above 40 °C. Afouda (1999)also studied different comb<strong>in</strong>ations of soil water and temperature regimes. He found thatwhen <strong>in</strong>oculated seeds are sown under stress conditions (daily temperature cycle of 33°C for 13 hr and 23 °C for 11 hr and plants watered twice a week) the disease <strong>in</strong>cidencewas 92% and seedl<strong>in</strong>g mortality was 68%. By contrast, sow<strong>in</strong>g <strong>in</strong>oculated seeds underapparently normal conditions (daily temperature cycle of 28 °C for 13 hr and 22 °C for11 hr, with plants watered regularly) resulted <strong>in</strong> disease <strong>in</strong>cidence of 15% and seedl<strong>in</strong>gmortality of 5%.Attempts to develop susta<strong>in</strong>able control options have focused mostly on seed treatmentswith fungicides and biological control agents. For example, Ramadose (1994) andArjunan and Raguchander (1996), <strong>in</strong> two <strong>in</strong>dependent studies <strong>in</strong> India, obta<strong>in</strong>ed goodcontrol of seedl<strong>in</strong>g blight by treat<strong>in</strong>g seeds with carbendazim or thiram. Another study(Latha et al. 1997) has shown that addition of ZnSO 4at 50 kg/ha to Zn deficient soil,significantly reduced Macrophom<strong>in</strong>a root rot, compared to untreated soil; apparently Znhad a fungicidal effect on the pathogen. The search for biocontrol agents has focused onTrichoderma spp. and Bacillus spp. Ushamal<strong>in</strong>i and his associates evaluated Trichodermaspp. first <strong>in</strong> vitro (Ushamal<strong>in</strong>i et al. 1997a) and then <strong>in</strong> field (Ushamal<strong>in</strong>i et al. 1997b) andobta<strong>in</strong>ed effective control <strong>in</strong> both cases with T. harzianum and T. viride. In pot experiments<strong>in</strong> Niger, Afouda (1999) evaluated 13 isolates of Bacillus subtilis and found isolate A11 tobe most promis<strong>in</strong>g. Thus, plants <strong>in</strong>fected with M. phaseol<strong>in</strong>a and treated with B. subtilisA11 showed the lowest blight <strong>in</strong>cidence of 13% and the highest percentage germ<strong>in</strong>ationof 72% compared to blight <strong>in</strong>cidence of 70% and germ<strong>in</strong>ation percentage of 40% forcheck, <strong>in</strong>oculated with M. phaseol<strong>in</strong>a. Also Ushamal<strong>in</strong>i et al. (1997c) have screened 21botanicals for their efficacy to <strong>in</strong>hibit the growth of M. phaseol<strong>in</strong>a under <strong>in</strong> vitro conditions.They showed that extracts of three plant species (Vitex negundo, Adenocalymmaalliaceum, and Ocimum sanctum) effectively <strong>in</strong>hibited mycelia growth and sclerotic germ<strong>in</strong>ationof M. phaseol<strong>in</strong>a. F<strong>in</strong>ally, efforts to f<strong>in</strong>d sources of resistance to M. phaseol<strong>in</strong>ahave cont<strong>in</strong>ued. For example, Mahabeer et al. (1995) evaluated 30 cowpea varieties <strong>in</strong>India and found that none was completely resistant while five were moderately resistant.In contrast, Rodrigues et al. (1997) reported that 10 cowpea genotypes <strong>in</strong> Brazil wereresistant to M. phaseol<strong>in</strong>a.To improve the efficiency of detect<strong>in</strong>g M. phaseol<strong>in</strong>a <strong>in</strong>fection of cowpea seed––importantfor plant quarant<strong>in</strong>e and plant<strong>in</strong>g seed certification purposes––Afouda (1999) raisedantibodies aga<strong>in</strong>st the cytosol and extracellular components of M. phaseol<strong>in</strong>a and usedthem <strong>in</strong> a double antigen sandwich ELISA (DAS-ELISA). He found that three of his fourantigens detected specifically M. phaseol<strong>in</strong>a <strong>in</strong> prote<strong>in</strong> extracts of the fungus as well as<strong>in</strong> samples from <strong>in</strong>fected plants. The most effective antigen (designated 848/3) detected15–30 ng/ml prote<strong>in</strong> extracts of M. phaseol<strong>in</strong>a but was less specific than the next mosteffective antigen (848/4) which has the advantage of not cross-react<strong>in</strong>g with any of then<strong>in</strong>e other fungi used <strong>in</strong> the sensitivity test (Afouda 1999).Diseases <strong>in</strong>duced by Colletotrichum speciesTwo major diseases of cowpea (anthracnose and brown blotch) are <strong>in</strong>duced by two dist<strong>in</strong>ctspecies of the genus Colletotrichum. Emechebe and Flor<strong>in</strong>i (1997), on the basis ofthe <strong>in</strong>formation available by September 1995, suggested that the cowpea anthracnosepathogen be regarded as a species that is dist<strong>in</strong>ct from C. l<strong>in</strong>demuthianum, the Phaseolus100

<strong>Recent</strong> <strong>advances</strong> <strong>in</strong> <strong>research</strong> on cowpea diseasesbean anthracnose pathogen. Indeed, Latunde-Dada et al. (1996) have provided strongevidence <strong>in</strong> favor of consider<strong>in</strong>g the cowpea anthracnose pathogen as a form of C.destructivum O’Gara. This has been accepted by the authors of a recent major review ofcowpea diseases (Allen et al. 1998). Cowpea brown blotch pathogen is C. capsici whileC. truncatum is presently considered to refer to the same fungus (Allen et al. 1998). New<strong>in</strong>formation from the relatively little <strong>research</strong> done on the two diseases <strong>in</strong> the past fiveyears is now presented.Us<strong>in</strong>g essentially the same methodology, Adebitan et al. (1996) and Adebitan andIkotun (1996) studied the effect of plant spac<strong>in</strong>g and cropp<strong>in</strong>g pattern on brown blotchand anthracnose at Ibadan (Nigeria). They reported a greater reduction of brown blotch <strong>in</strong>monocropped cowpea (Adebitan et al. 1996). It was shown that wide spac<strong>in</strong>g of cowpearesulted <strong>in</strong> lower <strong>in</strong>cidence and severity of brown blotch compared to the closer plantedcrop, both monocrop and <strong>in</strong>tercrop. As expected, similar results were obta<strong>in</strong>ed <strong>in</strong> theanthracnose trial. Anthracnose <strong>in</strong>cidence and severity were lower <strong>in</strong> the <strong>in</strong>tercrop relativeto the sole crop while reduction <strong>in</strong> both <strong>in</strong>ter- and <strong>in</strong>trarow spac<strong>in</strong>g resulted <strong>in</strong> an <strong>in</strong>crease<strong>in</strong> the <strong>in</strong>cidence and severity of anthracnose (Adebitan and Ikotun 1996). Adebitan (1996)has also evaluated the effects of weed <strong>in</strong>festation and application of phosphorus fertilizeron anthracnose. The severity of anthracnose was lowest <strong>in</strong> plots given 80 kg/ha P 2O 5andhighest <strong>in</strong> plots that did not receive phosphorus fertilizer. Also, plots kept weed-free untilharvest had 56.9% lower anthracnose <strong>in</strong>cidence and 43.2% lower severity when comparedto the unweeded check plot.Apart from these studies on effects of cultural practices, some attention was devotedto develop<strong>in</strong>g disease control options. Thus, Bankole and Adebanjo (1996) work<strong>in</strong>g <strong>in</strong>southwestern Nigeria, have reported that seed treatment or soil drench<strong>in</strong>g with dense(1 × 10 8 condia/ml) conidial suspension of Trichoderma viride effectively reduced brownblotch <strong>in</strong>fection. In addition, foliar application of spore suspension of T. viride once ortwice weekly, beg<strong>in</strong>n<strong>in</strong>g three days after <strong>in</strong>oculation of seedl<strong>in</strong>gs with the pathogen,reduced brown blotch <strong>in</strong> the field. The yield of plots sprayed twice weekly with suspensionof T. viride was not significantly different from that of plots sprayed weekly withbenomyl. Another study <strong>in</strong> Nigeria has shown that water or alcohol extract of Piper betle,Ocimum sanctum, and Citrus limon were effective <strong>in</strong> check<strong>in</strong>g the <strong>in</strong>cidence and spread ofanthracnose <strong>in</strong> the field. Extracts of P. betle were the most effective <strong>in</strong> both the laboratoryand the field (Amadioha 1999).Sphaceloma scabScab of cowpea is <strong>in</strong>duced by a Sphaceloma sp. (Emechebe 1980) which is usually regardedas the anamorph of the perfect species, Els<strong>in</strong>oe phaseoli Jenk<strong>in</strong>s. It is considered as themost important disease of cowpea wherever it occurs <strong>in</strong> both the northern and southernGu<strong>in</strong>ea savanna zones of West and Central Africa (Emechebe and Shoy<strong>in</strong>ka 1985). Itsoccurrence <strong>in</strong> East Africa has been confirmed by reports from Uganda (Iceduna et al.1994; Nakawuka and Adipala 1997; Edema et al. 1997). In Brazil, Central America, andSur<strong>in</strong>ame, it is one of the most destructive diseases of cowpea (L<strong>in</strong> and Rios 1985).Despite its importance, cowpea scab has received relatively little <strong>research</strong> attention. Inone of these studies, Nakawuka and Adipala (1997) found that 10 out of 75 cowpea genotypesevaluated <strong>in</strong> Uganda were resistant to the pathogen based on the foliar symptoms ofthe disease, while 24 were resistant based on pod <strong>in</strong>fection. In a separate experiment, thesame workers (Nakawuka and Adipala 1997) studied the nature of <strong>in</strong>heritance of resistance101

Cowpea <strong>in</strong>tegrated pest managementto Sphaceloma scab. Their data showed that additive genetic variance constituted the majorportion of the total genetic variance for resistance to scab <strong>in</strong> their varieties.Given the difficulty of isolat<strong>in</strong>g the pathogen from <strong>in</strong>fected tissue (Emechebe 1981)and the absolute necessity for artificial cultures for detailed work, Mungo et al. (1998a)recently developed a culture medium for easy isolation of the scab pathogen. The cowpeaisolate of Sphaceloma sp. appears to be restricted to cowpea (Vigna unguiculata); artificial<strong>in</strong>oculation of many species of legumes (<strong>in</strong>clud<strong>in</strong>g Vigna radiata, Phaseolus lunatus, andP. vulgaris) did not produce any symptoms with the exception of Lablab purpureus (hyac<strong>in</strong>thbean) (Emechebe 1981). The cowpea scab fungus, therefore, differs <strong>in</strong> pathogenicityfrom the isolate of Els<strong>in</strong>oe phaseoli reported by Jenk<strong>in</strong>s (1931) which has a much widerhost range, <strong>in</strong>clud<strong>in</strong>g P. vulgaris, V. radiata, and cowpea. <strong>Recent</strong>ly, it was reported thatSphaceloma occurred on n<strong>in</strong>e out of 14 major weed species found <strong>in</strong> cowpea fields <strong>in</strong> thenorthern Gu<strong>in</strong>ea savanna of Nigeria (Adebitan 1998). Apparently, isolates of Sphacelomasp. were obta<strong>in</strong>ed from scab lesions on these weeds and seven of them were pathogenic,to vary<strong>in</strong>g degrees, on cowpea. These f<strong>in</strong>d<strong>in</strong>gs do not imply that the plant species thatyielded the isolates are new hosts for the Sphaceloma sp. that <strong>in</strong>duces cowpea scab undernatural conditions. Rather, the results <strong>in</strong>dicate that cowpea is one of the hosts of the isolatesobta<strong>in</strong>ed from the seven weed species.Some work has been done on the epidemiology of the fungus. Mungo et al. (1998b)showed that <strong>in</strong>oculum for primary <strong>in</strong>fection under field conditions orig<strong>in</strong>ated either fromthe <strong>in</strong>fected seed or from <strong>in</strong>fected cowpea debris, with primary lesions appear<strong>in</strong>g onthe hypocotly or epicotyl (but not on the unifoliate primary leaves) about 25 days aftersow<strong>in</strong>g. Secondary spread of the fungus was by ra<strong>in</strong> splash and w<strong>in</strong>d-driven moisture.Earlier work (Emechebe 1980) had shown that cowpea scab development is exacerbatedby moderate temperatures (23–28 ºC), three or more consecutive days of wet weather,and consequent high relative humidity. These requirements probably partly expla<strong>in</strong> therecent report from Uganda by Edema et al. (1997) that the <strong>in</strong>cidence and severity of scabwere higher dur<strong>in</strong>g the second season. They also found that scab was favored by highplant populations (conducive for ra<strong>in</strong> splash dispersal) while grow<strong>in</strong>g cowpea <strong>in</strong> <strong>in</strong>trarowmixtures with other crops resulted <strong>in</strong> less disease.Diseases <strong>in</strong>duced by Thanatephorus cucumeris (Rhizoctonia solani)Thanatephorus cucumeris (Frank) Donk, usually occurr<strong>in</strong>g <strong>in</strong> nature and artificial culturemedia <strong>in</strong> its anamorphic state, Rhizoctonia solani Kuhn, is soilborne and ubiquitous. T.cucumeris has a broad host range and comprises about 12 anastamosis groups (AG), andit has been suggested that these groups be accorded taxonomic status (Allen et al. 1998).The fungus <strong>in</strong>duces two dist<strong>in</strong>ctly different diseases <strong>in</strong> cowpea––web blight and a rootrot/seedl<strong>in</strong>g disease complex––separated <strong>in</strong> time and space. Web blight is <strong>in</strong>duced byaerial types, usually belong<strong>in</strong>g to AG-1, while the stra<strong>in</strong>s that <strong>in</strong>duce root rots/seedl<strong>in</strong>gdiseases are strongly soilborne, <strong>in</strong> contrast to the aerial stra<strong>in</strong>, which has only a transientassociation with the soil. The two diseases are important throughout the humid tropicallowlands, and are regarded as major diseases <strong>in</strong> the forest belt of West Africa (Allen etal. 1998). They can also be severe under localized, waterlogged conditions <strong>in</strong> both moistand dry savanna regions. Similarly, web blight is destructive <strong>in</strong> Lat<strong>in</strong> America and <strong>in</strong>hot humid regions of India (L<strong>in</strong> and Rios 1985; Verma and Mishra 1989). The root andseedl<strong>in</strong>g phase results <strong>in</strong> root rot and <strong>in</strong> damp<strong>in</strong>g-off/seedl<strong>in</strong>g blight, the latter be<strong>in</strong>g due102

<strong>Recent</strong> <strong>advances</strong> <strong>in</strong> <strong>research</strong> on cowpea diseasesto collar/foot rot. Both phases of the disease complex are seed-transmitted (Emechebeand McDonald 1979).Publications of <strong>research</strong> efforts on diseases <strong>in</strong>duced by R. solani dur<strong>in</strong>g the period underreview have orig<strong>in</strong>ated from only two countries––India and Brazil. In all cases, the rootrot/seedl<strong>in</strong>g disease complex had been the target. Noronha et al. (1998) evaluated 20 genotypesof cowpea for their reaction to R. solani under both screenhouse and field conditions<strong>in</strong> Brazil. In the screenhouse, seeds were sown <strong>in</strong> sterilized soil that was artificially <strong>in</strong>oculatedwith the pathogen while <strong>in</strong> the field they were sown <strong>in</strong> naturally <strong>in</strong>fested field. Theirresults showed that none of the varieties was resistant <strong>in</strong> both environments, be<strong>in</strong>g eithermoderately susceptible or susceptible. In India, Sunder et al. (1996) studied the effectsof <strong>in</strong>oculum characteristics on pathogenicity of R. solani. They showed that an <strong>in</strong>crease<strong>in</strong> <strong>in</strong>oculum dose from 50 to 200 mg/pot resulted <strong>in</strong> an <strong>in</strong>crease <strong>in</strong> seedl<strong>in</strong>g mortality andthat the pathogenicity of the isolate decl<strong>in</strong>ed as the age of the <strong>in</strong>oculum <strong>in</strong>creased. Theirresults also revealed that <strong>in</strong>oculum grown at 25 °C or 30 °C and pH 6.5–7.5 producedhigher seedl<strong>in</strong>g mortality compared to <strong>in</strong>oculum cultivated at 20 °C or 35 °C.Efforts to develop control options concentrated on efficacy of biological control agentsand fungicides, both deployed as seed treatments. In Brazil, Noronha et al. (1995) screenedisolates of Bacillus subtilis for their efficacy aga<strong>in</strong>st R. solani as seed treatment <strong>in</strong> thescreenhouse and <strong>in</strong> the field. Initially 40 isolates of B. subtilis were tested aga<strong>in</strong>st oneisolate of the pathogen <strong>in</strong>oculum at a dose of 50 mg (of <strong>in</strong>oculum grown on rice gra<strong>in</strong>)per kg of potted soil. The best three isolates were then evaluated <strong>in</strong> pot culture aga<strong>in</strong>stfour isolates of R. solani, each at four <strong>in</strong>oculum levels of 50, 100, 200, and 300 mg/kg ofsoil. The most efficacious isolate of B. subtilis was f<strong>in</strong>ally evaluated <strong>in</strong> the field aga<strong>in</strong>stfour <strong>in</strong>oculum levels of the pathogen. In all cases, cowpea seeds were <strong>in</strong>oculated with B.subtilis by dipp<strong>in</strong>g <strong>in</strong> bacterial suspension conta<strong>in</strong><strong>in</strong>g 1 × 10 9 cell/ml. The results showedthat seed treatment with B. subtilis significantly reduced seedl<strong>in</strong>g mortality and was superiorto seed treatment with qu<strong>in</strong>tozene, a fungicide. Instead of B. subtilis isolates, those offluorescent Pseudomonas spp. were screened as seed treatment (seeds dipped <strong>in</strong> bacterialsuspension conta<strong>in</strong><strong>in</strong>g 1 × 10 8 cell/ml) aga<strong>in</strong>st R. solani also <strong>in</strong> Brazil by Barbosa et al.(1995), us<strong>in</strong>g a protocol remarkably similar to that of Noronha et al. (1995). The resultsshowed that one of the isolates of P. fl uorescens significantly reduced seedl<strong>in</strong>g mortality<strong>in</strong>duced by R. solani at all levels of pathogen <strong>in</strong>oculum tested, the level of control be<strong>in</strong>gsuperior to that obta<strong>in</strong>ed with seed treatment with the fungicide, qu<strong>in</strong>tozene. An evaluationof fungicidal seed treatments was conducted <strong>in</strong> India by Ram et al. (1995) who foundthat carbendazim and thiophanate-methyl were not only the most effective among sevenfungicides but they also significantly reduced seedl<strong>in</strong>g mortality, compared to the otherfungicides and the check.Cercospora and Pseudocercospora leaf spotsCercospora leaf spot is <strong>in</strong>duced by Cercospora canescens Ellis and Mart<strong>in</strong>, while Pseudocercosporaleaf spot is <strong>in</strong>duced by Mycosphaerella cruenta Latham <strong>in</strong> the form of itsanamorph, Pseudocercospora cruenta (Sacc.) Deighton, formerly C. cruenta (Emechebeand Shoy<strong>in</strong>ka 1985). Before C. cruenta was redesignated as P. cruenta, the diseases<strong>in</strong>duced by what were considered as two species of the genus, Cercospora were knownas Cercospora leaf spots. Pseudocercospora leaf spot is characterized by chlorotic ornecrotic spots on the upper leaf surface and profuse masses of conidiophores and conidia,103

Cowpea <strong>in</strong>tegrated pest managementappear<strong>in</strong>g as downy gray to black mats, on the lower leaf surface. Cercospora leaf spot ischaracterized mostly by circular to irregular cherry red to reddish-brown lesions on bothleaf surfaces. Both pathogens survive the no-crop period on <strong>in</strong>fected crop residue and <strong>in</strong><strong>in</strong>fected seed (Williams 1975; Patel 1985) although Emechebe and McDonald (1979)were unable to demonstrate seed-to-plant transmission of C. canescens. Both leaf spotshave been reported from all cowpea grow<strong>in</strong>g regions of the world. P. cruenta <strong>in</strong>duces leafspot on several legumes and C. canescens on an even wider range of legumes––the list ofsuscepts of each pathogen is provided by Allen et al. (1998). However Pseudocercosporaleaf spot is economically more important than Cercospora leaf spot.Emechebe and Flor<strong>in</strong>i (1997) noted that very little work on the two cowpea diseaseshad been done between 1985 and 1995. This situation did not change between 1995 and2000. The few reports that appeared dur<strong>in</strong>g this period focused on varietal resistance andfungicidal control. In Ch<strong>in</strong>a, 131 cowpea accessions were evaluated for their reaction to P.cruenta <strong>in</strong> the field subsequent to artificial <strong>in</strong>oculation (L<strong>in</strong> et al. 1995). It was shown that15 accessions were immune and seven were highly resistant. Although only six cowpeacultivars were evaluated <strong>in</strong> S<strong>in</strong>gapore by Le<strong>in</strong>a et al. (1996), one variety was found to behighly resistant to P. cruenta. In another experiment, Le<strong>in</strong>a et al. (1996) demonstrated adirect correlation between the variation <strong>in</strong> peroxidase activity <strong>in</strong> the soluble fraction of<strong>in</strong>oculated leaves and resistance to <strong>in</strong>fection <strong>in</strong> cowpea cultivars; they also showed thatthe soluble fraction of <strong>in</strong>oculated leaves had higher preoxidase activity than either themitochondrial or chloroplast extracts.Evaluation of fungicides for the control of Pseudocercospora leaf spot was conducted<strong>in</strong> Bangladesh and Nigeria. In Nigeria, Amadi (1995) evaluated three fungicides (benomyl,mancozeb, and captafol) for the control Cercospora leaf spot <strong>in</strong> Ilor<strong>in</strong>. He reported thatweekly spray<strong>in</strong>g of benomyl, beg<strong>in</strong>n<strong>in</strong>g at three weeks after plant<strong>in</strong>g, gave the best controlof the diseases and the highest gra<strong>in</strong> yield. A trial by Haque et al. (1994) <strong>in</strong> Bangladeshtested the efficacy of six fungicides aga<strong>in</strong>st Pseudocercospora leaf spot. Their resultsshowed that the best control of the disease and the highest gra<strong>in</strong> yield were obta<strong>in</strong>ed bythree to four sprays of benomyl after 12 days.Brown rustBrown rust is <strong>in</strong>duced by Uromyces appendiculatus (Pers) Unger (synonym: U. vignaeBarclay). It occurs <strong>in</strong> all cowpea produc<strong>in</strong>g areas of the world, <strong>in</strong> contrast to the localizedoccurrence of p<strong>in</strong>k rust, Phakospora spp. (P. pachyrhizi occurs <strong>in</strong> Cambodia, Ch<strong>in</strong>a,Ghana, Nigeria, and Sierra Leone while P. meibomiae occurs <strong>in</strong> Brazil.) Cowpea brownrust is considered a major disease <strong>in</strong> the ra<strong>in</strong>forest and southern Gu<strong>in</strong>ea savanna zonesof West Africa and <strong>in</strong> midaltitude areas of East Africa (Emechebe and Shoy<strong>in</strong>ka 1985).Konate and Ouedraogo (1988) have reported moderate to high <strong>in</strong>tensities of brown rust<strong>in</strong> the northern Gu<strong>in</strong>ea savanna of Burk<strong>in</strong>a Faso. Also Stofella et al. (1990) have shownthat brown rust is one of the most important fungal diseases of cowpea at Fort Pierce,Florida, USA. U. appendiculatus survives the period between corps as teliospores <strong>in</strong><strong>in</strong>fected crop residue.Although some authorities (e.g., Allen et al. 1998) question the global economicimportance of brown rust, the disease received the highest <strong>research</strong> attention amongthe fungal diseases of cowpea dur<strong>in</strong>g the 1995/2000 period. Several <strong>research</strong> areaswere covered, such as <strong>in</strong>oculation techniques, disease physiology, host-plant resistance,and mechanism of resistance, mutation breed<strong>in</strong>g, and cultural and fungicidal control.104

<strong>Recent</strong> <strong>advances</strong> <strong>in</strong> <strong>research</strong> on cowpea diseasesObviously, not all the papers on these topics are reviewed here; rather only a few paperson the various themes are considered. Among these themes, rust disease physiology wasgiven a lot of attention. For example, Heath (1998) studied the <strong>in</strong>volvement of reactiveoxygen species <strong>in</strong> hypersensitive response (HR) of cowpea to <strong>in</strong>fection by the rust.His results provided evidence that the rust fungi <strong>in</strong>itially negate nonspecific defensiveresponses <strong>in</strong> both resistant and susceptible cells as part of the establishment of biotrophy.His data also suggested that the HR <strong>in</strong> the cowpea–cowpea rust fungus pathosystem isnot triggered by an oxidative burst. In another study on the role of calcium <strong>in</strong> signaltransduction dur<strong>in</strong>g cowpea HR to brown rust, Xu and Heath (1998) demonstrated that theelevation of Ca 2+ ion level was <strong>in</strong>volved <strong>in</strong> signal transduction lead<strong>in</strong>g to the HR dur<strong>in</strong>grust fungal <strong>in</strong>fection. Another study <strong>in</strong> the same laboratory purified and characterized twonovel HR-<strong>in</strong>duc<strong>in</strong>g specific elicitors produced by the cowpea rust fungus and found thatthe two specific elicitors were products of two avirulence genes correspond<strong>in</strong>g to the twogenes for resistance <strong>in</strong> the resistant cultivar (D’-Silva and Heath 1997). The phenomenonof slow rust<strong>in</strong>g has also been detected <strong>in</strong> cowpea <strong>in</strong>fected by brown rust fungus <strong>in</strong> India(Cherian et al. 1996a, b).The genetics of resistance <strong>in</strong> a few cultivars have been determ<strong>in</strong>ed. A study of <strong>in</strong>heritanceof resistance <strong>in</strong> cultivar Calico Crowder has suggested the presence of dom<strong>in</strong>ant andrecessive resistance components (Ryerson and Heath 1996). In India, Rangaiah (1997)<strong>in</strong>vestigated the <strong>in</strong>heritance of resistance <strong>in</strong> a resistant cowpea genotype and showed thata m<strong>in</strong>imum of two genes control resistance. Brown rust control with fungicides was alsostudied <strong>in</strong> India by Kale and Anahosur (1996) who found that triadimefon and mancozebsprays effectively controlled brown rust <strong>in</strong> cowpea.Effective methods for artificial <strong>in</strong>oculation of cowpea with uredospores of U. appendiculatushave been described. Zeng et al. (1999) reported that <strong>in</strong> Ch<strong>in</strong>a the optimumconditions for host <strong>in</strong>fection consisted of spore concentration of 3.24 × 10 5 /ml and ambienttemperature of 23–26 ºC. They also found that good germ<strong>in</strong>ation of uredospores wasobta<strong>in</strong>ed <strong>in</strong> sterilized tap or distilled water conta<strong>in</strong><strong>in</strong>g 1% each of glucose and sucroseand leaf extract of cowpea seedl<strong>in</strong>g. Earlier, Kale and Anahosur (1994) effectively <strong>in</strong>oculatedcowpea with uredospore suspension by spray<strong>in</strong>g 45-day-old plants four times onalternate days.Other fungal diseasesResearch f<strong>in</strong>d<strong>in</strong>gs on other fungal diseases reported dur<strong>in</strong>g the period under review arepresented <strong>in</strong> Table 4.105

Cowpea <strong>in</strong>tegrated pest managementTable 4. Summary of <strong>research</strong> f<strong>in</strong>d<strong>in</strong>gs on some fungal diseases reported from 1995 toJuly 2000.Disease/pathogenMajor <strong>research</strong> f<strong>in</strong>d<strong>in</strong>gs/referenceBlack leaf spot or leaf Out of 156 genotypes evaluated for resistance tosmut (Protomycopsis E. vignae <strong>in</strong> Brazil, only 3 were resistant (Santosphaseoli Ramak. & et al. 1997).Subram. or Entyloma In vitro studies <strong>in</strong> Nigeria showed Trichodermavignae Batista)harzianum more effective than T. kon<strong>in</strong>gii and Trichodermasp. <strong>in</strong> reduc<strong>in</strong>g radial growth of P. phaseoli whilefield studies <strong>in</strong>dicated that Trichoderma sp. was betterthan T. kon<strong>in</strong>gii and T. harzianum (Adejumo et al. 1999 ) <strong>in</strong>the control of the leaf smut.Fusarium wilt (Fusarium Extracts of 3 out of 21 plant species <strong>in</strong>hibitedoxysporum f. sp. vas<strong>in</strong>fectum mycelia growth and spore germ<strong>in</strong>ation <strong>in</strong> India[E.F. Smith] Snyd. & Hans.) (Ushamal<strong>in</strong>i et al. 1997a).Greatest suppression of mycelia growth of wilt pathogenobta<strong>in</strong>ed with Bacillus subtilis followed byT. harzianum and Pseudomonas fluorescens (Ushamal<strong>in</strong>iet al. 1997b).Study of <strong>in</strong>teraction between F. oxysporum f.sp.tracheiphilum and Meloidogyne <strong>in</strong>cognita showed that:(1) Infection by M. <strong>in</strong>cognita did not predispose wiltresistant cowpea to wilt disease.(2) Wilt occurred <strong>in</strong> nematode-treated plots <strong>in</strong> wilt susceptiblevar.(3) Yield of wilt resistant genotypes reduced by about17% by nematode <strong>in</strong>fection <strong>in</strong> nontreated plot.(4) In nontreated plots yield of wilt susceptible genotypeswas reduced by about 37–65% by comb<strong>in</strong>ednematode and wilt <strong>in</strong>fections. (Roberts et al. 1995).Phytophthora stem rot or Cowpea <strong>in</strong>oculation with mycorrhizal fungi (Glomusred stem canker (P. vignae <strong>in</strong>traradices) could provide some degree of reductionPurss and P. cactorum of P. vignae stem and root rot disease <strong>in</strong> cowpea,[Leb. & Chon] Schroet) <strong>in</strong>dependent of nutritional or other growth effects <strong>in</strong>USA (Fernando and L<strong>in</strong>derman 1997).Sclerotium basal stem rot Out of 20 cowpea l<strong>in</strong>es evaluated for resistance toor wilt (Sclerotium rolfsii S. rolfsii, only one l<strong>in</strong>e was moderately resistant (MuqitSacc. [teliomorph = et al. 1996).Corticium rolfsii Curzi]) Six fungicides evaluated as seed treatment; vitax-200gave best control of C. rolfsii and highest gra<strong>in</strong> yield(Rahman et al. 1994).Pythium soft stem rot Two isolates each of Trichoderma viride and Bacillus(Pythium aphanidermatum cereus and 3 of B. subtilis evaluated <strong>in</strong> vitro and <strong>in</strong> vivo[Edson] Fitz)for efficacy aga<strong>in</strong>st P. aphanidermatum. T. viride hyperparasitizedpathogen mycelium while bacterial isolates<strong>in</strong>hibited it, <strong>in</strong> vitro. Applied as soil treatments, theantagonists reduced seedl<strong>in</strong>g <strong>in</strong>fection. Efficacy ofantagonists <strong>in</strong>creased with <strong>in</strong>crease <strong>in</strong> dose (Bankoleand Adebanjo 1998).106

<strong>Recent</strong> <strong>advances</strong> <strong>in</strong> <strong>research</strong> on cowpea diseasesViral diseasesIntroductionHampton et al. (1997) have listed n<strong>in</strong>e viruses considered most damag<strong>in</strong>g to cowpea,seven of which that are seedborne be<strong>in</strong>g the follow<strong>in</strong>g: blackeye cowpea mosaic potyvirus(BlCMV), cowpea aphid-borne mosaic potyvirus (CABMV), cucumber mosaicvirus (CMV), cowpea mosaic comovirus (CPMV), cowpea severe mosaic comovirus(CPSMV), southern bean mosaic sobemovirus (SBMV), and cowpea mottle carmovirus(CPMoV). The two nonseedborne viruses considered important by Hampton et al.(1997) are cowpea golden mosaic gem<strong>in</strong>ivirus (CGMV) and cowpea chlorotic mottlebromovirus (CCMV). They listed about eight other viruses considered to be of m<strong>in</strong>or orundeterm<strong>in</strong>ed importance. Major <strong>research</strong> f<strong>in</strong>d<strong>in</strong>gs on eight of the n<strong>in</strong>e viruses publisheddur<strong>in</strong>g the past five years are summarized below. We found no specific publication onCGMV dur<strong>in</strong>g the period.Blackeye cowpea mosaic potyvirus (BlCMV)BlCMV occurs wherever the crop is grown. It is particularly damag<strong>in</strong>g when it occurs <strong>in</strong>comb<strong>in</strong>ation with other viruses (Hampton et al. 1997). Based on the number of publicationson it, BlCMV has received fairly good attention from <strong>research</strong>ers dur<strong>in</strong>g the periodunder review.<strong>Recent</strong> reports have confirmed the occurrence of BlCMV <strong>in</strong> northeast Asia (Reeves1997), Indonesia (Hadiastono 1996), and Sri Lanka (Premala et al. 1996). It appears thatthere are several sources of genetic resistance among cowpea genotypes. Thus, Bashirand Hampton (1996) evaluated only 51 cultivars and l<strong>in</strong>es for resistance to seven geographicallyand pathologically diverse isolates of BlCMV <strong>in</strong> Pakistan and found five to beimmune to all isolates and three immune to all but one of the isolates. Another study <strong>in</strong> theUSA (Hunter et al. 1996) has shown that it is possible to screen cowpea simultaneously forresistance to the virus and Meloidogyne <strong>in</strong>cognita. However, mixed <strong>in</strong>fection of BlCMVand cucumber mosaic virus (CMV) resulted <strong>in</strong> severe cowpea stunt disease symptoms andhigh concentration of CMV coat prote<strong>in</strong> 20 days after <strong>in</strong>oculation of all plants withoutextreme resistance to BlCMV (Anderson et al. 1996). It seems that resistance to BlCMVdeterm<strong>in</strong>ed through symptom observation is not adequate when evaluat<strong>in</strong>g germplasmfor cowpea stunt resistance and that rapid development of symptoms on dually <strong>in</strong>fectedplants may not be due solely to <strong>in</strong>creased CMV concentration. On the other hand, when45 and 54 seedborne isolates of BlCMV and cowpea aphid-borne mosaic virus (CABMV),respectively, were compared us<strong>in</strong>g various serological tests and def<strong>in</strong>itive host reactions,isolates of BlCMV were clearly dist<strong>in</strong>guished serologically from CABMV isolates (Bashirand Hampton 1996). Although isolate comparison on selected cowpea genotypes partitionedmost isolates <strong>in</strong>to two dist<strong>in</strong>ct groups, a few isolates from seeds of a particularcowpea variety were def<strong>in</strong>itely BlCMV by all serological tests but behaved as CABMV<strong>in</strong> def<strong>in</strong>itive cowpea genotypes. <strong>Recent</strong>ly, Boxtel et al. (2000) found that 10 elite l<strong>in</strong>es ofcowpea differed widely <strong>in</strong> their susceptibility to both BlCMV and CABMV and did notalways show correlation between field performance and resistance to virus <strong>in</strong>fection underglasshouse conditions. The importance of high seedborne transmission of BlCMV suggeststhat <strong>in</strong> addition to control through HPR, some control could be obta<strong>in</strong>ed by productionand plant<strong>in</strong>g virus-free seeds as suggested for Taiwan by Chang et al. (1994).107

Cowpea <strong>in</strong>tegrated pest managementCowpea aphid-borne mosaic potyvirus (CABMV)CABMV is widely distributed <strong>in</strong> the world and causes severe crop losses either alone or<strong>in</strong> comb<strong>in</strong>ation with other viruses (Hampton et al. 1997). Based on the number of publicationson it, CABMV has received the greatest attention from <strong>research</strong>ers. The occurrenceof CABMV on cowpea grown commercially <strong>in</strong> the USA was reported <strong>in</strong> 1997 (Kl<strong>in</strong>e andAnderson 1997). <strong>Recent</strong> reports have also confirmed its occurrence <strong>in</strong> Zimbabwe (Gubba1994) and Nepal (Dahal and Albrechtsen 1996).To facilitate diagnosis of CABMV <strong>in</strong>fections, especially its dist<strong>in</strong>ction from BlCMV,Bashir and Hampton have developed a procedure for purify<strong>in</strong>g isolates of the two viruses(Bashir and Hampton 1995) and standardized both the direct antigen coat<strong>in</strong>g ELISA(DAC-ELISA) and double antibody sandwich ELISA (DAS-ELISA) (Bashir et al. 1995).However, large-scale surveys for BlCMV and CABMV showed that several CABMV isolatesfrom Southern Africa were either poorly or not recognized by monoclonal antibodiesprepared for isolates collected <strong>in</strong> West Africa (Huguenot et al. 1996). Consequently, threenew monoclonal antibodies prepared aga<strong>in</strong>st the Maputo (Mozambique) isolates were<strong>in</strong>cluded <strong>in</strong> a revised panel of monoclonal antibodies, result<strong>in</strong>g <strong>in</strong> assignment of isolatesto appropriate serotypes, <strong>in</strong>clud<strong>in</strong>g a newly created serotype (Huguenot et al. 1996).Another contribution to improved diagnosis is a rapid technique for detect<strong>in</strong>g CABMVfrom cowpea seeds developed by Konate and Neya (1996) <strong>in</strong> Burk<strong>in</strong>a Faso.As a first step <strong>in</strong> develop<strong>in</strong>g resistant varieties, cowpea genotypes have been screenedfor their reaction <strong>in</strong> several countries. In Pakistan, Muhammad et al. (1996) screened 51l<strong>in</strong>es aga<strong>in</strong>st seven isolates of CABMV and found three immune. Similarly Kannan andDoraiswamy (1994) detected 30 immune l<strong>in</strong>es out of the 50 evaluated by them.Cowpea mosaic comovirus (CPMV)CPMV is considered to be one of the most important cowpea viruses <strong>in</strong> Africa (Hamptonet al. 1997). Most of the work reported dur<strong>in</strong>g the last five years focused on the molecularcomponents and their functions. Lekkerkerker et al. (1996) studied the functional doma<strong>in</strong>sof the movement prote<strong>in</strong> (MP) and found that it conta<strong>in</strong>s at least two dist<strong>in</strong>ct doma<strong>in</strong>s,one that is <strong>in</strong>volved <strong>in</strong> tubule formation and a second that is <strong>in</strong>volved <strong>in</strong> the <strong>in</strong>corporationof the virus particle <strong>in</strong>to the tubule. Subsequent work of Kasteel et al. (1997) revealedthat apart from the MP and the capsid prote<strong>in</strong>s (CP) of CPMV, no other <strong>in</strong>fection-specificprote<strong>in</strong>s existed <strong>in</strong> the <strong>in</strong>fected tissue. This agrees with recent f<strong>in</strong>d<strong>in</strong>gs of Verver etal. (1998) that both CP and the MP are absolutely required for cell-to-cell movement ofCPMV. A study <strong>in</strong> India has demonstrated that transmission of CPMV by Myzus persicaerequires: (1) a 24-hr <strong>in</strong>oculation feed<strong>in</strong>g period, (2) optimum acquisition period of 10m<strong>in</strong>, (3) pre-acquisition fast<strong>in</strong>g of one hour, and (4) a m<strong>in</strong>imum of eight aphids per plant(Nagaraju and Murthy 1997).As noted by Hampton et al. (1997), the best and most practical method of control ofCPMV is the use of resistant cultivars. In this regard, Nagaraju and Keshavamurthi (1998)have reported that eight out of 20 l<strong>in</strong>es were resistant to CPMV.Cucumber mosaic cucumovirus (CMV)Despite its common and widespread occurrence (through both seed and aphid transmission)CMV is considered a mild cowpea pathogen, except <strong>in</strong> <strong>in</strong>fection-sensitive genotypesor when comb<strong>in</strong>ed with BlCMV (Hampton et al. 1997). However, Gillaspie et al. (1998)have reported a new seedborne stra<strong>in</strong> of CMV that <strong>in</strong>duces severe symptoms on many108

<strong>Recent</strong> <strong>advances</strong> <strong>in</strong> <strong>research</strong> on cowpea diseasescowpea genotypes <strong>in</strong> Georgia (USA). This stra<strong>in</strong> [CMV-Csb] is symptomatic on tobaccobut it produces more severe cowpea stunt symptoms when present <strong>in</strong> comb<strong>in</strong>ation withBlCMV than do the more prevalent CMV isolates.The detailed structure of CMV has been determ<strong>in</strong>ed by Wikoff et al. (1997), and itis very similar to that of cowpea chlorotic mosaic virus. Other workers have shown thatthe RNA2 of CMV is <strong>in</strong>volved <strong>in</strong> resistance break<strong>in</strong>g <strong>in</strong> cowpea (Jang et al. 1996). Mostcowpea genotypes are resistant to stra<strong>in</strong> Y of CMV (CMV-Y), the resistance be<strong>in</strong>g dependenton existence of a resistance (R) gene <strong>in</strong> these genotypes. Nasu et al. (1996) have foundthat <strong>in</strong>heritance of HR as a component of the resistance to CMV-Y <strong>in</strong> these a genotypes(typified by Kurodane Sanjaku cultivar of Japan) is controlled by a s<strong>in</strong>gle dom<strong>in</strong>ant gene.Another component of the resistance to CMV <strong>in</strong> most cowpea genotypes, apart from HR,is the localization of systemic <strong>in</strong>fection. The results of a recent study by Kim et al. (1997)have suggested that an <strong>in</strong>hibition response <strong>in</strong> protoplasts, where an HR does not occur,leads to a localization of <strong>in</strong>fection <strong>in</strong> the whole plant and that different cowpea genes are<strong>in</strong>volved <strong>in</strong> elicit<strong>in</strong>g the HR and the localization response. It is <strong>in</strong>terest<strong>in</strong>g that <strong>in</strong>ductionof resistance to CMV by apply<strong>in</strong>g the systemic fungicide, ferimzone, has been attributedto the production of salicylic acid <strong>in</strong> the treated plants (Nakayama et al. 1996)Cowpea chlorotic mottle bromovirus (CCMV)CCMV can cause heavy crop damage <strong>in</strong> susceptible cowpea cultivars, alone or <strong>in</strong> mixed<strong>in</strong>fections (Hampton et al. 1997). Although it has been isolated from two weed species<strong>in</strong> Nigeria (Thottappilly et al. 1993), CCMV <strong>in</strong>fection of cowpea <strong>in</strong> nature appears to beconf<strong>in</strong>ed to North and South America (Hampton et al. 1997). Most of the work reporteddur<strong>in</strong>g the period under review was targeted at understand<strong>in</strong>g the molecular basis for<strong>in</strong>fection and viral movement with<strong>in</strong> the <strong>in</strong>fected plant. Jong et al. (1997) concluded thatunder normal circumstances, the rate of CCMV cell-to-cell spread <strong>in</strong> cowpea is limitedprimarily by factors other than the movement prote<strong>in</strong>. In this regard, Schneider et al. (1997)found that virion formation is not required for systemic <strong>in</strong>fection and that the carboxyltwo thirds of the CP is required and sufficient for systemic movement of the viral RNA.They suggested that the CP of CCMV is multifunctional, with a dist<strong>in</strong>ct, long-distancemovement function and a role <strong>in</strong> virion formation. Rao (1997) has also concluded thatCCMV moves <strong>in</strong> a nonvirion form. The molecular basis for reduction <strong>in</strong> virulence <strong>in</strong>the stra<strong>in</strong> (CCMV-T) that produces <strong>in</strong>tense and extensive chlorosis to that <strong>in</strong> the stra<strong>in</strong>(CCMV-M) that produces mild symptoms has been provided by Filho et al. (2000). Theyfound that the genetic determ<strong>in</strong>ants of symptom expression is located <strong>in</strong> the third portionof the coat prote<strong>in</strong> gene––specifically, am<strong>in</strong>o acid residue Ala 151 <strong>in</strong> CMV-T is changedto Val 151 <strong>in</strong> the CCMV-M.Cowpea mottle carmovirus (CPMoV)CPMoV was first isolated <strong>in</strong> Nigeria by Shoy<strong>in</strong>ka et al. (1978). S<strong>in</strong>ce that time it has beenreported from Ben<strong>in</strong>, Côte d’Ivoire, Pakistan, and Togo (Hampton et al. 1997). It appearsthat the only publication specifically devoted to CPMoV was by Gillaspie et al. (1999).They described sensitive reverse transcription-polymerase cha<strong>in</strong> reaction (RT-PCR)method for detection of CPMoV <strong>in</strong> newly acquired cowpea germplasm. The RT-PCRmethod was up to 10 5 times more sensitive than direct action coat<strong>in</strong>g ELISA (DAC-ELISA)<strong>in</strong> detect<strong>in</strong>g CPMoV and gave no false positive reaction as is seen sometimes with ELISA(Gillaspie et al. 1999).109

Cowpea <strong>in</strong>tegrated pest managementSouthern bean mosaic sobemovirus (SBMV)The cowpea stra<strong>in</strong> of SBMV (SBMV-C) often occurs <strong>in</strong> mixtures with other beetle-transmittedviruses, <strong>in</strong>clud<strong>in</strong>g CCMV and CPSMV (Hampton et al. 1997). The few publicationson SBMV-C dur<strong>in</strong>g the last five years were devoted to its molecular structure and functions.Thus, Hacker (1995) has identified the location of the CP b<strong>in</strong>d<strong>in</strong>g site (between nucleotide1410 and 1436) on the SBMV-C genome. Later, Hacker and Sivakumara (1997) reportedon the mapp<strong>in</strong>g and expression of SBMV genomic and subgenomic RNAs. The sameworkers (Sivakumaran et al. 1998) have identified the viral genes needed for cell-to-cellmovement of SBMV-C. They found that open read<strong>in</strong>g frames 1 and 3 (ORF1 and ORF3)prote<strong>in</strong>s and the CP are required for SBMV-C cell-to-cell movement.Cowpea severe mosaic comovirus (CPSMV)The symptoms of CPSMV <strong>in</strong> some cowpea genotypes are similar to those of CPMV butthese symptoms, contrary to the term “severe”, may not be more severe than those ofCPMV. Accord<strong>in</strong>g to Hampton et al. (1997), CPSMV comprises at least n<strong>in</strong>e serotypes andan unknown number of pathogenic variants. Given this extent of pathogenic variation, itis not surpris<strong>in</strong>g that a large proportion of the few, new publications were on HPR-related<strong>research</strong>. In Brazil, 181 cowpea genotypes were screened for their reaction to CPSMVand five genotypes were found to be immune and n<strong>in</strong>e genotypes resistant (Paz et al.1999). Umaharan et al. (1997b) reported that four cowpea genotypes were immune, onewas tolerant, and three were resistant (out of 160 evaluated) to the Tr<strong>in</strong>idad isolate. Withrespect to <strong>in</strong>heritance of resistance, Umaharan (1997a) found that <strong>in</strong> Tr<strong>in</strong>idad resistancewas controlled by three major genes and that resistance was gene dosage dependent.However, Vale and Lima (1995) attributed control of immunity <strong>in</strong> variety Macaibo to as<strong>in</strong>gle recessive gene.An unusual <strong>in</strong>teraction between CPMV and CPSMV has been reported from Canada(Eastwell and Kalmar 1997). In certa<strong>in</strong> cowpea cultivars immune to CPMV, co<strong>in</strong>oculationof CPMV with CPSMV stra<strong>in</strong> DG reduced severity and delayed symptoms normally<strong>in</strong>duced by CPSMV. In cultivars susceptible to both viruses, co<strong>in</strong>oculation delays developmentof symptoms <strong>in</strong> response to CPSMV. The data by Eastwell and Kalmar (1997)revealed that the presence of CPMV <strong>in</strong> the <strong>in</strong>oculum resulted <strong>in</strong> a concomitant delay <strong>in</strong>synthesis of CPSMV coat prote<strong>in</strong> and replication of CPSMV RNA and restricted thetransport of CPSMV out of <strong>in</strong>fection centers.Cowpea parasitic nematodesThe comprehensive list of nematodes parasitic on cowpea compiled by Caveness andOgunfowora (1985) conta<strong>in</strong>ed 51 species <strong>in</strong> 23 genera. Flor<strong>in</strong>i (1997) <strong>in</strong>dicated n<strong>in</strong>e speciesreported on cowpea between 1985 and 1995. Although there have been a reasonablenumber of publications on plant parasitic nematodes between 1995 and 2000, about 50%of these publications have been devoted to Meloidogyne spp., with the rest focus<strong>in</strong>g mostlyon Rotylenchulus reniformis and Heterodera cajani. Other species previously recordedon cowpea but referred to rather <strong>in</strong>cidentally are Paratrichodorus m<strong>in</strong>or, Pratylenchussp., Xiph<strong>in</strong>ema sp. Criconemella spp., Hoplolaimus pararobustus, and Aphasmatylenchusstraturatus.Aphasmatylenchus straturatus and A. variabilis were found <strong>in</strong> Senegal by Baujard andMart<strong>in</strong>y (1995a). The two species appeared <strong>in</strong>capable of enter<strong>in</strong>g anhydrobiosis necessaryfor survival of dry conditions of the Sahel. Only A. straturatus was pathogenic <strong>in</strong> cowpea110

<strong>Recent</strong> <strong>advances</strong> <strong>in</strong> <strong>research</strong> on cowpea diseasesbut relatively high soil populations of more than 1000 nematodes per plant were required.Similarly, Hoplolaimus pararobustus was pathogenic <strong>in</strong> cowpea <strong>in</strong>duc<strong>in</strong>g reduction <strong>in</strong>cowpea root fresh weight also at relatively high soil populations (Baujard and Mart<strong>in</strong>y1995b). The rest of this section reviews appropriate publications on Meloidogyne <strong>in</strong>cognita,Rotylenchulus reniformis, and Heterodera cajani.Meloidogyne spp.By far the most important of the species of Meloidogyne pathogenic <strong>in</strong> cowpea is M. <strong>in</strong>cognita(Sarmah and S<strong>in</strong>ha 1995; Khan et al. 1996). M. javanica has also been reported, but itis far less pathogenic than M. <strong>in</strong>cognita (Puruthi et al. 1995). To identify resistance sources,several <strong>research</strong>ers have screened cowpea genotypes for their reaction to Meloidogyne spp.In India, Subramaniyan et al. (1997) identified only three out of 37 l<strong>in</strong>es as resistant to M.<strong>in</strong>cognita. By contrast eight out of n<strong>in</strong>e cultivars were rated as resistant <strong>in</strong> Cuba (Rodriguezet al. 1996); <strong>in</strong> Venezuela one out of eight varieties was resistant to Meloidogynespp (Renato et al. 1995). A related study on genetics of <strong>in</strong>heritance (Roberts et al. 1996)<strong>in</strong>dicated that resistance <strong>in</strong> IT84S-2049 is governed by one dom<strong>in</strong>ant nuclear gene.Attempts have been made to evaluate several plant-derived materials for the control ofMeloidogyne spp. <strong>in</strong> cowpea. In Nigeria, Onifade and Fawole (1996) demonstrated thatextract from Anacardium occidentale was the most efficacious aga<strong>in</strong>st M. <strong>in</strong>cognita, theleast effective be<strong>in</strong>g the extract from Gmel<strong>in</strong>a arborea. A pot culture study <strong>in</strong> India hasshown that add<strong>in</strong>g chopped green leaves of neem (Azadirachta <strong>in</strong>dica) and of Eupatoriumsp. effectively controlled M. <strong>in</strong>cognita. Similarly, <strong>in</strong> Egypt, <strong>in</strong>corporat<strong>in</strong>g different typesof crop residue <strong>in</strong>to the soil about one week before soil <strong>in</strong>oculation with M. <strong>in</strong>cognitawas more effective than residue <strong>in</strong>corporated at the time of soil <strong>in</strong>oculation (Youssef andAm<strong>in</strong> 1997). Efforts at biological control <strong>in</strong>clude those of Azmi (1995) who obta<strong>in</strong>edgood control of M. <strong>in</strong>cognita with predacious nematodes <strong>in</strong> India as well as those ofYoussef and Ali (1998) who controlled M. <strong>in</strong>cognita with a mixture of three species <strong>in</strong>three genera of native blue green algae. As expected, nematicides have been screened forthe control of Meloidogyne spp. For example, of several nematicides evaluated <strong>in</strong> Indiaas seed treatment for the control of M. <strong>in</strong>cognita, carbosulfan at 0.05 or 0.1% soak for 6hours or monocrotophos at 0.1% soak (also for 6 hours) was effective (Kumar 1996). InEgypt, fenamiphos 10% granular was more effective than soil amendment with organicmatter (residue) derived from both cereals and legumes (Youssef and Am<strong>in</strong> 1997).Interaction between Meloidogyne spp. on the one hand and beneficial microorganismsand other soilborne plant pathogens on the other were reported dur<strong>in</strong>g the periodunder review. Kassab and Ali (1996) <strong>in</strong>vestigated <strong>in</strong>teractions among M. <strong>in</strong>cognita,Rotylenchulus reniformis, Rhizoctonia solani, and Rhizobium. They showed additive<strong>in</strong>teraction (result<strong>in</strong>g <strong>in</strong> reduced germ<strong>in</strong>ation and seed emergence) between R. solaniand any of the nematodes. Inoculation with M. <strong>in</strong>cognita alone slightly promoted plantgrowth and nodulation, both of which were suppressed by <strong>in</strong>oculation with R. reniformisalone. R. solani alone severely damaged plant growth and suppressed nodulation and when<strong>in</strong>oculated with M. <strong>in</strong>cognita, there was <strong>in</strong>crease <strong>in</strong> both gall<strong>in</strong>g and nematode fecundity.Comb<strong>in</strong>ed <strong>in</strong>oculation of R. solani and R. reniformis resulted <strong>in</strong> R. solani be<strong>in</strong>g parasiticbut not pathogenic to cowpea, without affect<strong>in</strong>g life cycle and fecundity of R. reniformis.An experiment <strong>in</strong> the USA studied the <strong>in</strong>teractions between virulent M. <strong>in</strong>cognita andFusarium wilt on resistant cowpea genotypes (Roberts et al. 1995). It was shown that111

Cowpea <strong>in</strong>tegrated pest management<strong>in</strong>fection by M. <strong>in</strong>cognita did not predispose wilt-resistant genotypes to wilt disease. Inwilt-susceptible genotypes, wilt occurred <strong>in</strong> nematicide-treated plots and was exacerbatedby nematode <strong>in</strong>fection <strong>in</strong> nontreated plots, regardless of the presence of wilt resistancegene. The yield of wilt-resistant genotypes was reduced by about 17%, on the average,as a result of nematode <strong>in</strong>fection while that of wilt-susceptible genotypes was reduced by37–65% because of comb<strong>in</strong>ed effects of nematode and wilt <strong>in</strong>fections.Interactions between Meloidogyne spp. and mycorrhizal fungi have also receivedattention. Santhi et al. (1995) studied the <strong>in</strong>teractions between M. <strong>in</strong>cognita and threespecies of the mycorrhizal fungal genus, Glomus (G. fasciculatus, G. versiforme, and G.etunicatus). Their data revealed that G. fasciculatus was the most effective at reduc<strong>in</strong>gthe nematode population <strong>in</strong> the soil. The <strong>in</strong>fluence of three levels of phosphorus on the<strong>in</strong>teraction between VAM fungi and M. <strong>in</strong>cognita has been <strong>in</strong>vestigated <strong>in</strong> India (Santhiand Sundarababu 1995). It was found that plants with VAM were more resistant to M.<strong>in</strong>cognita than those without; there was a positive correlation between nematode levelsand nematode populations and a negative correlation between phosphorus levels and theVAM spore population and root colonization.Rotylenchulus reniformisThe work published on cowpea–R. reniformis pathosystem dwelt mostly with host–parasite<strong>in</strong>teractions and control. Cowpea genotypes have been shown to be good hosts of R.reniformis <strong>in</strong> India (Rao and Ganguly 1996) and Egypt (Am<strong>in</strong> and Youssef 1997; Kassaband Ali 1996). Control of R. reniformis by soil amendments with organic matter has beenreported for chopped leaves of neem and Eupatorium <strong>in</strong> India (Ajith and Sheela 1996) andfor various crop residues <strong>in</strong> Egypt (Youssef and Am<strong>in</strong> 1997). Nematicides have also beenevaluated for the control of R. reniformis and effective controls reported for fenamiphosand monocrotophos applied as seed treatments <strong>in</strong> India (Rathore and Yadav 1996) andfor soil-applied granular formulations of Aldicarb 10G and Carbofuran 3G, also <strong>in</strong> India(Rathore 1995).Heterodera cajaniOnly a few publications on H. cajani were apparently produced dur<strong>in</strong>g the last five years.It has been demonstrated <strong>in</strong> India that cowpea is an efficient host of H. cajani (Sharmaet al. 1996). Cowpea’s host efficiency has been exploited <strong>in</strong> the control of H. cajani onpigeon pea <strong>in</strong> which cowpea is used as a green manure <strong>in</strong>corporated <strong>in</strong>to the soil at fourweeks after sow<strong>in</strong>g, thereby <strong>in</strong>duc<strong>in</strong>g reduction of populations of juvenile stages of H.cajani and the consequent <strong>in</strong>crease <strong>in</strong> gra<strong>in</strong> yield of pigeon pea (Rathore 1995).The hatch<strong>in</strong>g and <strong>in</strong>fectivity of second juvenile stage of H. cajani under vary<strong>in</strong>g soilmoisture, relative humidity, and storage period were <strong>in</strong>vestigated <strong>in</strong> India (Gaur et al. 1996).Cysts were stored at between 0 and 100% relative humidity (RH) for up to three weeksor <strong>in</strong> moist or air-dried soil for up to 12 months. It was found that desiccation reducedbut did not completely <strong>in</strong>hibit hatch<strong>in</strong>g of cyst. Eggs with<strong>in</strong> cysts withstood extremes ofdesiccation. Cysts stored <strong>in</strong> moist soil for up to 12 months had a greater percentage cysthatch <strong>in</strong> cowpea root diffusate than those from air-dried soil. Egg hatch occurred up tofirst four months of storage <strong>in</strong> moist compared to first two months <strong>in</strong> air-dried soil.112

<strong>Recent</strong> <strong>advances</strong> <strong>in</strong> <strong>research</strong> on cowpea diseasesParasitic flower<strong>in</strong>g plantsAmong crop plants, cowpea is perhaps unique <strong>in</strong> be<strong>in</strong>g severely attacked by two species<strong>in</strong> two genera of parasitic angiosperms, namely Striga gesnerioides (Willd.) Vatke andAlectra vogelii (L.) Benth. Both were <strong>in</strong>cluded <strong>in</strong> the review by S<strong>in</strong>gh and Emechebe(1997) but only S. gesnerioides featured <strong>in</strong> the reviews by Lane et al. (1997) and Allenet al. (1998). Although both parasites constitute severe constra<strong>in</strong>ts to cowpea production<strong>in</strong> most of the grow<strong>in</strong>g regions <strong>in</strong> sub-Saharan Africa, S. gesnerioides is considered themore important of the two (Emechebe et al. 1991; Lagoke et al. 1994). The cowpea stra<strong>in</strong>of S. gesnerioides attacks only cowpea but there are wild stra<strong>in</strong>s that attack legum<strong>in</strong>ousshrubs while two other stra<strong>in</strong>s attack tobacco and sweetpotato <strong>in</strong> certa<strong>in</strong> parts of Africa.Populations of A. vogelii on cowpea cause serious damage to groundnut, moderate <strong>in</strong>fections<strong>in</strong> bambara groundnut, and occasional <strong>in</strong>fection of soybean.Research effort on cowpea Striga published between mid-1995 and mid-2000 has beendevoted to HPR, histopathology, sources of suicidal germ<strong>in</strong>ation, and the physiology ofthe effect of N on Striga <strong>in</strong>fection of cowpea. Reiss and Bailey (1998) studied the processof <strong>in</strong>fection of cowpea by S. gesnerioides. They showed that penetration of host corticalcells by the cone-shaped Striga endophyte is accomplished through <strong>in</strong>tercellular growthfacilitated by gentle dissolution of the middle lamella.Pathogenic variation with<strong>in</strong> and among populations of S. gesnerioides does not appearto have changed dur<strong>in</strong>g the period under review, s<strong>in</strong>ce there is no evidence of the existenceof more than the five races described by Lane et al. (1997). However Race 4 (socalled Zakpota stra<strong>in</strong>) has been detected <strong>in</strong> Kazaure, Gumel, and Birn<strong>in</strong> Kuddu <strong>in</strong> JigawaState of Nigeria (Emechebe et al. 1999) while the newest race (Race 5) has been found <strong>in</strong>Maradi (Niger) by Toure et al. (1998) <strong>in</strong> addition to its previously documented occurrence<strong>in</strong> Ben<strong>in</strong>, Burk<strong>in</strong>a Faso, Cameroon, and Nigeria (Lane et al. 1996). Fortunately sourcesof resistance gene to race 5 (landraces 87-2 and APL1) have been identified (Moor etal. 1995) and have been <strong>in</strong>corporated <strong>in</strong>to popular varieties (B.B. S<strong>in</strong>gh 1999, personalcommunication).The strategy for Striga control is the reduction of the population of Striga seeds <strong>in</strong> thesoil. One way of accomplish<strong>in</strong>g this is to <strong>in</strong>duce Striga seeds to germ<strong>in</strong>ate <strong>in</strong> the absenceof the host with the subsequent death of the Striga seedl<strong>in</strong>g. In this respect, Berner andWilliams (1998) evaluated cultivars of more than 20 crop species for their capacity to<strong>in</strong>duce germ<strong>in</strong>ation of seeds of S. gesnerioides <strong>in</strong> vitro. They found that genotypes of allVigna spp. evaluated as well as some genotypes of Cajanus cajan, Lablab purpureus,Sphenostylis stenocarpa, and Sorghum bicolor <strong>in</strong>duced germ<strong>in</strong>ation of seeds of S. gesnerioides.However, it has been suggested by Berner and Williams (1998) that S. gesnerioidescontrol <strong>in</strong>volv<strong>in</strong>g rotation with nonhost cultivars has potential for success only if thesecultivars are selected with the Striga isolate(s) from the locality of <strong>in</strong>tended deploymentof the nonhost cultivar. Ethylene gas has been used to stimulate germ<strong>in</strong>ation of S. asiatica<strong>in</strong> the absence of the host. In a recent report, Berner et al. (1999) presented data that suggestedthat some ethylene-produc<strong>in</strong>g stra<strong>in</strong>s of Pseudomonas syr<strong>in</strong>gae pv. glyc<strong>in</strong>ea weremore effective than ethylene <strong>in</strong> stimulat<strong>in</strong>g germ<strong>in</strong>ation of seeds of three species of Striga,<strong>in</strong>clud<strong>in</strong>g S. gesnerioides. Although this is scientifically <strong>in</strong>terest<strong>in</strong>g, it is unlikely to haveany direct practical application <strong>in</strong> the control of any of the species s<strong>in</strong>ce the bacterium isthe pathogen of soybean bacterial blight, a serious pathogen of soybean––an importantcrop <strong>in</strong> production systems of the areas of potential use.113

Cowpea <strong>in</strong>tegrated pest managementAn estimate of the yield loss due to Striga <strong>in</strong>fection of cowpea under natural conditionswas provided by Muleba et al. (1997). They studied yield losses <strong>in</strong> cowpea genotypes ofvary<strong>in</strong>g susceptibility to cowpea Striga under Striga-<strong>in</strong>fested and Striga-free conditions.They found that yield losses <strong>in</strong> Striga-<strong>in</strong>fested plots varied from 3.1% at the experimentstation to 44.2% <strong>in</strong> farmers’ fields. Also, depend<strong>in</strong>g on the susceptibility of the cowpeagenotypes to Striga, the yield loss varied from 3.1% to 36.5%. These losses are attributedto the adverse effects of Striga <strong>in</strong>fection on the host. The effect of Striga <strong>in</strong>fectionon cowpea photosynthesis was reported by Hibberd et al. (1996). They showed that theallometric relationship between shoot and root dry weight was similar <strong>in</strong> parasitized plantsrelative to the control plants, as was the proportion of the dry matter partitioned <strong>in</strong>to leaf,stem, and root tissues. However, <strong>in</strong>fected plants failed to make any significant <strong>in</strong>vestmentof dry matter <strong>in</strong> pods. The rate of photosynthesis of the youngest, fully expandedleaf of <strong>in</strong>fected plants was significantly lower than that of control plants. The lower rateof photosynthesis was not attributed to stomatal limitation, a loss of chlorophyll, or to anaccumulation of carbohydrates. The depression of photosynthesis <strong>in</strong> the young leaves wastransient. As control leaves aged, photosynthesis decl<strong>in</strong>ed. This also occurred <strong>in</strong> Striga<strong>in</strong>fected plants but to a lesser extent, result<strong>in</strong>g <strong>in</strong> higher rate of photosynthesis <strong>in</strong> matureleaves when compared to those of un<strong>in</strong>fected plants.ReferencesAdebitan, S.A. 1996. Effect of phosphorus and weed <strong>in</strong>terference on anthracnose of cowpea <strong>in</strong>Nigeria. Forage Research 22(1): 11–19.Adebitan, S.A. 1998. Record of new host plants for Sphaceloma on cowpea <strong>in</strong> Nigeria.Mycopathologia 143(1): 47–51.Adebitan, S.A., B. Fawole, and G.L. Hartman. 1996. Effect of plant spac<strong>in</strong>g and cropp<strong>in</strong>g patternon brown blotch (Colletotrichum truncatum) of cowpea. Tropical Agriculture 73: 275–280.Adebitan, S.A. and T. Ikotun. 1996. Effect of plant spac<strong>in</strong>g and cropp<strong>in</strong>g pattern on anthracnose(Colletotrichum l<strong>in</strong>demuthianum) of cowpea. Fitopatologia Brasileira 21(1): 5–12.Adejumo, T.O., T. Ikotun, and D.A. Flor<strong>in</strong>i. 1999. Biological control of Protomycopsis phaseoli,the causal agent of leaf smut of cowpea. Journal of Phytopathology 147(6): 371–375.Afouda, L.A.C. 1999. Approach to biological control of Macrophom<strong>in</strong>a phaseol<strong>in</strong>a (Tassi) Goid,causal agent of charcoal rot of cowpea (Vigna unguiculata [L.] Walp.) and development of serologicalmethods for its detection. PhD dissertation, Georg-August University, Goett<strong>in</strong>t<strong>in</strong>gen.Cuvillier Verlag, Goett<strong>in</strong>gen. 139 pp.Ajith, K. and M.S. Sheela. 1996. Utilization of green leaves of neem and Eupatorium for the managementof soil organisms <strong>in</strong> bh<strong>in</strong>di and cowpea. India Journal of Nematology 26(2): 139–143.Allen, D.J. and J.M. Lenne. 1998. Diseases as constra<strong>in</strong>ts to production of legumes <strong>in</strong> agriculture.Pages 1–61 <strong>in</strong> The pathology of food and pasture legumes, edited by D.J. Allen and J.M. Lenne.CAB International, Wall<strong>in</strong>gford, UK.Allen, D.J., G. Thottappilly, A.M. Emechebe, and B.B. S<strong>in</strong>gh. 1998. Diseases of cowpea. Pages267–324 <strong>in</strong> The pathology of food and pasture legumes, edited by D.J. Allen and J.M. Lenne.CAB International, Wall<strong>in</strong>gford, UK.Amadi, J.E. 1995. Chemical control of Cercospora leaf spot disease of cowpea (Vigna unguiculata[L.] Walp.). Agrosearch 1(2): 101–107.Amadioha, A.C. 1999. Evaluation of some plant leaf extracts aga<strong>in</strong>st Colletotrichum l<strong>in</strong>demuthianum<strong>in</strong> cowpea. Archives of Phytopathology and Plant Protection 32(2): 141–149.Am<strong>in</strong>, W.A. and M.M.A. Youssef. 1997. Host status effect of cowpea and sunflower on the populationsof Meloidogyne javanica and Rotylenchulus reniformis. Anzeiger fur Schadl<strong>in</strong>gskunde,Pflazenschutz, Umweltschutz 70(4): 75–76.114

<strong>Recent</strong> <strong>advances</strong> <strong>in</strong> <strong>research</strong> on cowpea diseasesAmusa, N.A. and R.U. Okechukwu. 1998. Reaction of selected cowpea (Vigna unguiculata [L.]Walp.) breed<strong>in</strong>g l<strong>in</strong>es to Xanthomonas campestris pv. vignicola. Tropical Agricultural Researchand Extension 1(2): 162–164.Anderson, E.J., A.S. Kl<strong>in</strong>e, T.E. Morelock, and R.W. McNew. 1996. Tolerance to blackeye cowpeamosaic potyvirus not correlated with decreased virus accumulation or protection from cowpeastunt disease. Plant Disease 80(8): 847–832.Arjunan, G. and T. Raguchander. 1996. Effect of seed treatment on root rot of cowpea. IndianJournal of Pulses Research 9(1): 83–84.Avel<strong>in</strong>g, T.A.S. and A. Adandonon. 2000. First report of pre-and post-emergence damp<strong>in</strong>g-off ofcowpea caused by Pythium ultimum <strong>in</strong> South Africa. Plant Disease Reporter 84(8): 922.Azmi, M.I. 1995. Control of root knot and root-lesion nematodes on cowpea and maize throughpredacious nematode complex <strong>in</strong> pots. Advances <strong>in</strong> Agricultural Research <strong>in</strong> India 3: 108–118.Bankole, S.A. and A. Adebanjo. 1996. Biocontrol of brown blotch of cowpea caused by Colletotrichumtruncatum with Trichoderma viride. Crop Protection 15(7): 633–636.Bankole, S.A. and A. Adebanjo. 1998. Efficacy of some fungal and bacterial isolates <strong>in</strong> controll<strong>in</strong>gwet rot disease of cowpea caused by Pythium aphanidermatum. Journal of Plant Protection <strong>in</strong>the Tropics 11(1): 37–43.Barbosa, M.A.G., S J.Michereff, R.L.R. Mariano, and E. Maranhao. 1995. Biocontrol of Rhizoctoniasolani <strong>in</strong> cowpea by seed treatment with fluorescent Pseudomonas spp. Summa Phytopathologica21(2): 151–157.Bashir, M. and R.O. Hampton. 1995. Purification and electron microscopy of some isolates ofblackeye cowpea mosaic and cowpea aphid-borne mosaic potyvirus. Pakistan Journal of Botany27(1): 243–249.Bashir, M. and R.O. Hampton. 1996. Serological and biological comparisons of blackeye cowpeamosaic and cowpea aphid-borne mosaic potyvirus isolates <strong>in</strong> Vigna unguiculata (L.) Walp.germplasm. Journal of Phytopathology 144(5): 257–263.Bashir, M., R.O. Hampton, and B. Muhammad. 1995. Antiserum production aga<strong>in</strong>st cowpea aphidbornemosaic virus and standardization of enzyme-l<strong>in</strong>ked immunosorbent assays. Sarhad Journalof Agriculture 11(4): 505–512.Baujard, P. and B. Mart<strong>in</strong>y. 1995a. Ecology and pathogenicity of the Hoplolaimidae (Nemata) fromthe sahelian zone of West Africa. 4. The genus Aphasmatylenchus Sher. Fundamental and AppliedNematology 18(4): 355–360.Baujard, P. and B. Mart<strong>in</strong>y. 1995b. Ecology and pathogenicity of the Hoplolaimidae (Nemata) fromthe sahelian zone of West Africa. 6. Hoplolaimus pararobustus (Schuurmans Stekhoven andTeunissen, 1938) Sher, 1963 and comparison with Hoplolaimus se<strong>in</strong>horsti Luc, 1958. Fundamentaland Applied Nematology 18(5): 435–444.Berner, D.K. and O.A. Williams. 1998. Germ<strong>in</strong>ation stimulation of Striga gesnerioides seeds byhosts and nonhosts. Plant Disease 82(11): 1242–1249.Berner, D.K., N.W. Schaad, and B. Volksch. 1999. Use of ethylene-produc<strong>in</strong>g bacteria for stimulat<strong>in</strong>gof Striga spp. seed germ<strong>in</strong>ation. Biological Control 15(3): 274–282.van Boxtel, J., B.B. S<strong>in</strong>gh, G. Thottapilly, and A.J. Maule. 2000. Resistance of cowpea (Vignaunguiculata [L.] Walp.) breed<strong>in</strong>g l<strong>in</strong>es to Blackeye cowpea mosaic and Cowpea aphid-bornemosaic potyvirus isolates under experimental conditions. Journal of Plant Disease and Protection107(2): 197–204.Bradbury, J.F. 1986. Xanthomonas Dowson 1939, 187. Pages 198–260 <strong>in</strong> Guide to plant pathogenicbacteria. CAB International Mycological Institute, Slough, England.Caveness, F.E. and A.O. Ogunfowora. 1985. Nematological studies worldwide. Pages 273–285 <strong>in</strong>Cowpea <strong>research</strong>, production and utilization, edited by S.R. S<strong>in</strong>gh and K.O. Rachie. John Wileyand Sons, Chichester, UK.Chang, C.A., T.T. Yang, T.M. Tsan, and C.C. Chen. 1994. Production and application of virus freeseeds to control virus diseases of asparagus beans. Plant Protection Bullet<strong>in</strong> (Taipei) 36(4):313–325.Cherian, S., T.B. Anilkumar, and V.V. Shulladmath. 1996a. Evaluation of slow rust<strong>in</strong>g <strong>in</strong> cowpeagermplasm. Mysore Journal of Agricultural Sciences 30(4): 374–379.115

Cowpea <strong>in</strong>tegrated pest managementCherian, S., T.B. Anilkumar, and V.V. Sulladmath. 1996b. Slow rust<strong>in</strong>g resistance <strong>in</strong> cowpea. MysoreJournal of Agricultural Sciences 30(2): 153–158.Dahal, G. and S.E. Albrechtsen. 1996. Some studies <strong>in</strong> cowpea aphid-borne mosaic and pea seedbornemosaic potyviruses <strong>in</strong> Nepal. International Journal of Pest Management 42(4): 337–344.D’-Silva, I. and M.C. Heath. 1997. Purification and characterization of two novel hypersensitiveresponse-<strong>in</strong>duc<strong>in</strong>g specific elicitors produced by the cowpea rust fungus. Journal of BiologicalChemistry 272(7): 3924–3927.Eastwell, K.C. and G.B. Kalmar. 1997. Characteriz<strong>in</strong>g the <strong>in</strong>terference between two comoviruses<strong>in</strong> cowpea. Journal of the American Society for Horticultural Science 122(2): 163–168.Edema, R., E. Adipala, and D.A. Flor<strong>in</strong>i. 1997. Influence of season and cropp<strong>in</strong>g system on occurrenceof cowpea diseases <strong>in</strong> Uganda. Plant Disease 81(5): 465–468.Emechebe, A.M. 1980. Scab disease of cowpea (Vigna unguiculata) caused by a species of thefungus Sphaceloma. Annals of Applied Biology 96: 11–16.Emechebe, A.M. 1981. Brown blotch of cowpea <strong>in</strong> northern Nigeria. Samaru Journal of AgriculturalResearch 1(1): 20–26.Emechebe, A.M. and D.A. Flor<strong>in</strong>i. 1997. Shoot and pod diseases of cowpea <strong>in</strong>duced by fungi andbacteria. Pages 176–192 <strong>in</strong> Advances <strong>in</strong> cowpea <strong>research</strong>, edited by B.B. S<strong>in</strong>gh, D.R. MohanRaj, K.E. Dashiell, and L.E.N. Jackai. Copublication of International Institute of Tropical Agriculture(IITA) and Japan International Research Center for Agricultural Science (JIRCAS). IITA,Ibadan, Nigeria.Emechebe, A.M. and D. McDonald. 1979. Seed-borne pathogenic fungi and bacteria of cowpea <strong>in</strong>northern Nigeria. PANS 25(4): 401–404.Emechebe, A.M. and S.A. Shoy<strong>in</strong>ka. 1985. Fungal and bacteria diseases of cowpea <strong>in</strong> Africa. Pages173–192 <strong>in</strong> Cowpea <strong>research</strong>, production and utilization, edited by S.R. S<strong>in</strong>gh and K.O. Rachie,John Wiley and Sons, Chichester, UK.Emechebe, A.M., B.B. S<strong>in</strong>gh, O.I. Leleji, I.D.K. Atokple, and J.K. Adu. 1991. Cowpea Strigaproblems and <strong>research</strong> <strong>in</strong> Nigeria. Pages 18–28 <strong>in</strong> Combat<strong>in</strong>g Striga <strong>in</strong> Africa, edited by S.K.Kim. IITA, Ibadan, Nigeria.Emechebe, A.M., J.P. Voh, O.O. Olufajo, and M.C. Dike. 1999. Report of 1998 Activities ofPEDUNE-Nigeria. IAR/ABU, Zaria, Nigeria.Fernando, W.G.D and R.G. L<strong>in</strong>derman. 1997. The effect of mycorrhizal (Glomus <strong>in</strong>traradisces)colonization on the development of root and stem rot (Phytophthora vignae) of cowpea. Journalof the Natural Science Council of Sri Lanka 25(1): 39–47.Filho, F.M.A., O.R. Paguio, J.L. Sherwood, and C.M. Deom. 2000. Mapp<strong>in</strong>g a symptom determ<strong>in</strong>antof cowpea chlorotic mottle virus. Phytopathology 90(6) Supplement: 125.Flor<strong>in</strong>i, D.A. 1997. Nematodes and other soilborne pathogens of cowpea. Pages 193–206 <strong>in</strong> Advances<strong>in</strong> cowpea <strong>research</strong>, edited by B.B. S<strong>in</strong>gh, D.R. Mohan Raj, K.E. Dashiell, and L.E.N. Jackai.Copublication of International Institute of Tropical Agriculture (IITA) and Japan InternationalResearch Center for Agricultural Science (JIRCAS). IITA, Ibadan, Nigeria.Gaur, H.S., J. Beans, and R.N. Perry. 1996. Effect of storage <strong>in</strong> vitro and <strong>in</strong> soil on the hatch fromcysts of pigeonpea cyst nematode, Heterodera cajani. Fundamental and Applied Nematology19(6): 537–544.Gillaspie, A.G. Jr., M.R. Hajimorad, and S.A. Ghabrial 1998. Characterization of a severe stra<strong>in</strong> ofcucumber mosaic cucumovirus seedborne <strong>in</strong> cowpea. Plant Disease 82(4): 419–422.Gillaspie, A.G. Jr, S.E. Mitchell, G.W. Stuart, and R.F. Bozarth. 1999. RT-PCR method for detect<strong>in</strong>gcowpea mottle carmovirus <strong>in</strong> Vigna germplasm. Plant Disease 83(7): 639–643.Grange, N.L.A. and T.A.S. Avel<strong>in</strong>g. 1998. First report of Alternaria cassiae on cowpea. PlantDisease 82(10): 1171.Gubba, A. 1994. Identification of cowpea viruses <strong>in</strong> Zimbabwe. Zimbabwe Journal of AgriculturalResearch 32(2): 149–155.116

<strong>Recent</strong> <strong>advances</strong> <strong>in</strong> <strong>research</strong> on cowpea diseasesHacker, D.L. 1995. Identification of a coat prote<strong>in</strong> b<strong>in</strong>d<strong>in</strong>g site on southern bean mosaic virus RNA.Virology (New York) 207(2): 562–565.Hacker, D.L. and K. Sivakumara. 1997. Mapp<strong>in</strong>g and expression of southern bean mosaic virusgenomic and subgenomic RNAS. Virology (New York) 234(2): 317–327.Hadiastono, T. 1996. A mosaic virus on blackeye cowpea (Vigna unguiculata [L.] Walp.). Agrivita19(3): 118–120.Hampton, R.O., G. Thottappilly, and H.W. Rossel. 1997. Viral diseases of cowpea and their controlby resistance-conferr<strong>in</strong>g genes. Pages 159–175 <strong>in</strong> Advances <strong>in</strong> cowpea <strong>research</strong>, edited by B.B.S<strong>in</strong>gh, D.R. Mohan Raj, K.E. Dashiell, and L.E.N. Jackai. Copublication of International Instituteof Tropical Agriculture (IITA) and Japan International Research Center for Agricultural Science(JIRCAS). IITA, Ibadan, Nigeria.Haque, M.S., M.L. Rahman, and M.A. Malek.1994. Effect of fungicides and number of sprays onCercospora leaf spot of cowpea. Bangladesh Journal of Plant Pathology 10(1–2): 3–4.Heath, M.C. 1998. Involvement of reactive oxygen species <strong>in</strong> the response of resistant (hypersensitive)or susceptible cowpeas to the cowpea rust fungus. New Phytologist 138(2): 251–263.Hibberd, J.M., W.P. Quick, M.C. Press, and J.D. Scholes. 1996. The <strong>in</strong>fluence of the parasiticangiosperm Striga gesnerioides on the growth and photosynthesis of its host, Vigna unguiculata.Journal of Experimental Botany 47(297): 507–512.Huguenot, C., M.T. Furneaux, J.A. Clare, and R.I. Hamilton. 1996. Improved diagnosis of cowpeaaphid-borne mosaic virus <strong>in</strong> Africa. Archives of Virology 141(1): 137–145.Huguenot, C., M.T. Furneaux, and R.I. Hamilton. 1997. Further characterization of cowpea aphidbornemosaic and blackeye cowpea mosaic potyviruses. Pages 231–239 <strong>in</strong> Advances <strong>in</strong> cowpea<strong>research</strong>, edited by B.B. S<strong>in</strong>gh, D.R. Mohan Raj, K.E. Dashiell, and L.E.N. Jackai. Copublicationof International Institute of Tropical Agriculture (IITA) and Japan International Research Centerfor Agricultural Science (JIRCAS). IITA, Ibadan, Nigeria.Hunter, A.G., O.L. Chambliss, and J.C. Williams. 1996. Simultaneous screen<strong>in</strong>g for resistance toblackeye cowpea mosaic virus and root knot nematode <strong>in</strong> southernpea. HortScience 31(7):1217–1218.Iceduna, L.C., E. Adipala, and M.W. Ogenga-Latigo. 1994. Evaluation of 80 cowpea l<strong>in</strong>es forresistance to scab, Sphaceloma sp. African Crop Science Journal 2: 207–217.Jang, H.S., Y.D. Choi, and C.H. Kim. 1996. Nucleotide sequence and <strong>in</strong>fectivity of cucumber mosaicvirus stra<strong>in</strong> B RNA2 <strong>in</strong>volved <strong>in</strong> resistance breakage on cowpea. Molecules and Cells 6(6):704–711.Jenk<strong>in</strong>s, A.M. 1931. Lima bean scab caused by Els<strong>in</strong>oe. Journal of Agricultural Research 42: 13–23.Jong, W., K. Mise, A. Chu, and P. Ahlquist. 1997. Effects of coat prote<strong>in</strong> mutations and reducedmovement prote<strong>in</strong> expression on <strong>in</strong>fection spread of cowpea chlorotic mottle virus and its hybridderivatives. Virology (New York) 232(1): 167–173.Kale, J.K. and K.H. Anahosur.1994. Evaluation of cowpea genotypes for rust resistance. KarnatakaJournal of Agricultural Sciences 7(1): 87–88.Kale, J.K. and K.H. Anahosur. 1996. Chemical control of cowpea rust. Karnataka Journal of AgriculturalSciences 9(1): 179–181.Kannan, N.R. and S. Doraiswamy. 1994. Screen<strong>in</strong>g cowpea entries for seed-borne <strong>in</strong>fection ofCAMV and to study the weed hosts of the virus. Madras Agricultural Journal 81(11): 637–638.Kassab, A.S. and M.K. Ali. 1996. Interaction among Meloidogyne <strong>in</strong>cognita, Rotylenchulusreniformis, Rhizoctonia solani, and Rhizobium on cowpea. Annals of Agricultural Sciences(Cairo) 41(1): 521–531.Kasteel, D.T.J., J. Well<strong>in</strong>k, R.W. Goldbach, and J.M.W. van Lent. 1997. Isolation and characterizationof tubular structure of cowpea mosaic virus. Journal of General Virology 78(12):3167–3170.117

Cowpea <strong>in</strong>tegrated pest managementKhan, M.R., M.W. Khan, and A.A. Khan. 1996. Effect of Meloidogyne <strong>in</strong>cognita on dry weight,root gall and root nodulation of chickpea and cowpea cultivars. Test of Agrochemicals andCultivars 17: 70–71.Khatri-Chhetri, G., K. Wydra, and K. Rudolph. 1998a. Characterization of Xanthomonas campestrispv. vignicola stra<strong>in</strong>s by metabolic f<strong>in</strong>gerpr<strong>in</strong>ts (BIOLOG system). International Congress of PlantPathology, Ed<strong>in</strong>burgh 1998. Abstract 2.2.103.Khatri-Chhetri, G., K. Wydra, and K. Rudolph. 1998b. Development of semi-selective medium forquick and easy isolation of Xanthomonas campestris pv. vignicola, <strong>in</strong>citant of cowpea bacteriablight and pustule. Mitteilung Biologische Bundesanstalt 357: 247.Kim, C., P. Palukaitis, and C.H. Kim. 1997. The plant defence response to cucumber mosaic virus<strong>in</strong> cowpea is elicited by the viral polymerase gene and affects virus accumulation <strong>in</strong> s<strong>in</strong>gle cells.EMBO Journal 16: 4060–4068.Kl<strong>in</strong>e, A.S. and E.J. Anderson. 1997. First report of cowpea aphid-borne mosaic potyvirus formcowpea grown commercially <strong>in</strong> the US. Plant Disease 81(8): 959.Konate, G. and B.J. Neya. 1996. Rapid detection of cowpea aphid-borne mosaic virus <strong>in</strong> cowpeaseed. Annals of Applied Biology 129(2): 261–266.Konate, G. and J. Ouedraogo. 1988. Cowpea pathology <strong>in</strong> Burk<strong>in</strong>a Faso, with particular emphasison viral diseases. Pages 51–52 <strong>in</strong> State of cowpea <strong>research</strong> <strong>in</strong> semi-arid zones of West and CentralAfrica, edited by N. Muleba and A.M. Emechebe. IITA/SAFGRAD, Ouagadougou, Burk<strong>in</strong>aFaso.Kumar, S. 1996. Efficacy of systemic <strong>in</strong>secticides as seed soak<strong>in</strong>g for the control of Meloidogyne<strong>in</strong>cognita on cowpea. Madras Agricultural Journal 83(8): 538–539.Lagoke, S.T.O., J.Y. Shebayan, G. Weber, O. Olufajo, K. Elemo, J.K. Adu, A.M. Emechebe, B.B.S<strong>in</strong>gh, A. Zaria, A. Awad, L. Ngawa, G.O. Olaniyan, S.O. Olafare, and A.A. Adeoti. 1994. Surveyof Striga problems and evaluation of Striga control methods and packages <strong>in</strong> crops <strong>in</strong> the Nigeriansavanna. Pages 91–120 <strong>in</strong> Improv<strong>in</strong>g Striga management <strong>in</strong> Africa. Proceed<strong>in</strong>gs, SecondGeneral Workshop of Pan-African Striga Control Network (PASCON), edited by S.T.O. Legoke,R. Hoevers, S.S. M’boob, and R. Traboulsi, 23–29 June 1991, Nairobi, Kenya. FAO/PASCON,Accra, Ghana.Lane, J.A., T.M.H. Moore, D.V. Child, and K.F. Cardwell. 1996. Characterization of virulence andgeographic distribution of Striga gesnerioides on cowpea <strong>in</strong> West Africa. Plant Disease 80(3):299–301.Lane, J.A., T.M.H. Moore, D.V. Child, and J.A. Bailey. 1997. Variation <strong>in</strong> virulence of Strigagesnerioides on cowpea: new sources of crop resistance. Pages 225–230 <strong>in</strong> Advances <strong>in</strong> cowpea<strong>research</strong>, edited by B.B. S<strong>in</strong>gh, D.R. Mohan Raj, K.E. Dashiell, and L.E.N. Jackai. Copublicationof International Institute of Tropical Agriculture (IITA) and Japan International Research Centerfor Agricultural Science (JIRCAS). IITA, Ibadan, Nigeria.Latha, K.R., D. Alice, R.O. S<strong>in</strong>gh, and S.R. Durai.1997. Effect of Zn on the development of rootrot of summer pulses. Madras Agricultural Journal 84(6): 340–342.Latunde-Dada, A.O., R.J. O’Connell, C. Nash, R.J. Prong, J.A. Luis, and J.A. Bailey. 1996. Infectionprocess and identity of the hemibiotrophic anthracnose fungus (Colletrichum destructivum)from cowpea (Vigna unguiculata). Mycological Research 100(9): 1133–1141.Latunde-Dada, A.O., R.J. O’Connell, C. Nash, and J.A. Lucas. 1999. Stomatal penetration of cowpea(Vigna unguiculata) leaves by Colletrotrichum species caus<strong>in</strong>g latent anthracnose. Plant Pathology48(6): 777–785.Le<strong>in</strong>a, M.J., T.K. Tan, and S.M. Wong. 1996. Resistance of Hibiscus esculentus L. and Vigna s<strong>in</strong>ensis(L.) Endl. to Pseudocercospora and plant peroxidase activity <strong>in</strong> relation to <strong>in</strong>fection. Annalsof Applied Biology 129(2): 197–206.Lekkerkerker, A., J. Well<strong>in</strong>k, P. Juan, J. van Lent, R. Goldbach, and A.B. Kammen. 1996. Dist<strong>in</strong>ctfunctional doma<strong>in</strong>s <strong>in</strong> the cowpea mosaic virus movement prote<strong>in</strong>. Journal of Virology 70(8):5658–5661.118

<strong>Recent</strong> <strong>advances</strong> <strong>in</strong> <strong>research</strong> on cowpea diseasesL<strong>in</strong>, M.C., H.P. Chen, Y.F. Wang, and W.Z. Zhang. 1995. Evaluation of cowpea varieties resistantto cowpea leaf mould (Cercospora cruenta Sacc.). Crop Genetic Resources 4: 36–37.L<strong>in</strong>, M.T. and G.P. Rios. 1985. Cowpea diseases and their prevalence <strong>in</strong> Lat<strong>in</strong> America. Pages199–204 <strong>in</strong> Cowpea <strong>research</strong>, production and utilization edited by K.O. Rachie and S.R. S<strong>in</strong>gh.John Wiley and Sons, Chichester, UK.Mahabeer, S., J.P. Agniotri, and M. S<strong>in</strong>gh. 1995. Screen<strong>in</strong>g of cowpea genotypes aga<strong>in</strong>st Macrophom<strong>in</strong>aphaseol<strong>in</strong>a. Indian Journal of Mycology and Plant Pathology 25(3): 324.Maramba, P. 1983. Plant pathology notes. Zimbabwe Agricultural Journal 80(1): 23.Mar<strong>in</strong>ga, I.K., D. Giga, and P. Maramba. 1985. Cowpea production constra<strong>in</strong>ts and <strong>research</strong> <strong>in</strong>Zimbabwe. Tropical Gra<strong>in</strong> Legume Bullet<strong>in</strong> 30: 9–14.Moore, T.H.M., J.A. Lane, D.V. Child, G.H. Arnold, J.A. Bailey, and G. Hofman. 1995. New sourcesresistance of cowpea (Vigna unguiculata) to Striga gesnerioides, a parasitic angiosperm.Euphytica 84(3): 165–174.Muhammad, B., R.O. Hampton, and M. Bashir. 1996. Sources of genetic resistance <strong>in</strong> cowpea(Vigna unguiculata [L.] Walp.) to cowpea aphid-borne mosaic potyvirus. European Journal ofPlant Pathology 102(5): 411–419.Muleba, N., J.T. Ouedraogo, and J.B. Tignegre. 1997. Crop yield loss attributed to Striga <strong>in</strong>festations.Journal of Agricultural Science 129(1): 43–48.Mungo, C.N., A.M. Emechebe, and D.A. Flor<strong>in</strong>i. 1998a. Isolation of Sphaceloma sp. from cowpeaplant parts us<strong>in</strong>g eight media. Crop Protection 17(4): 341–343.Mungo, C.N., A.M. Emechebe, and D.A. Flor<strong>in</strong>i. 1998b. The effect of cropp<strong>in</strong>g history and therole of cowpea debris <strong>in</strong> the epidemiology of cowpea scab. Plant Pathology 47(5): 595–600.Munoz, M.A. and M.P.J. Tamayo. 1994. The presence of Choanephora cucurbitarum <strong>in</strong> cowpea(Vigna unguiculata [L.] Walp.). ASCOLFI-Informa 20(1): 4–5.Muqit, A., M.S. Haque, and M.M. Hossa<strong>in</strong>. 1996. Reaction of cowpea l<strong>in</strong>es aga<strong>in</strong>st Sclerotiumrolfsii. Bangladesh Journal of Plant Pathology 12(1–2): 63.Nagaraju, N. and K.V.K. Murthy. 1997. Studies on the relationship between cowpea mosaic virusand its vector Myzus persicae Sulz. Mysore Journal of Agricultural Sciences 31(2): 170–174.Nagaraju, U. and K.V. Keshavamurthi. 1998. Varietal reaction of cowpea cultivars to mosaic diseaseof cowpea. Current Research––University of Agricultural Sciences (Bangalore) 27(1): 10–11.Nakawuka, C.J. and E. Adipala. 1997. Identification of sources and <strong>in</strong>heritance of resistance toSphaceloma scab <strong>in</strong> cowpea. Plant Disease 81(12): 1395–1399.Nakayama, M., K. Matsuura, and T. Okuno. 1996. Production of salicylic acid <strong>in</strong> tobacco and cowpeaplants by a systemic fungicide ferimzone and <strong>in</strong>duction of resistance to virus <strong>in</strong>fection. Journalof Pesticide Science 21(1): 69–72.Nasu, Y., A. Karasawa, S. Hase, and Y. Ehara. 1996. Cry, the resistance locus of cowpea to cucumbermosaic virus stra<strong>in</strong> Y. Phytopathology 86(9): 946–951.Noronha, M.A., S.J. Michereff, and R.L.R. Mariano. 1995. Effect of cowpea seed treatment withBacillus subtilis on Rhizoctonia solani control. Fitopatologia Brasileira 20(2): 174–178.Noronha, M.A., S.J. Michereff, and R.L. Mariano. 1998. Selection of common beans (Phaseolusvulgaris) and cowpea (Vigna unguiculata) germplasms resistant to Rhizoctonia solani. Bolet<strong>in</strong>Micologica 13(1–2): 111–116.Onifade, A.K. and B. Fawole.1996. Effect of some plant extracts on the pathogenicity of Meloidogyne<strong>in</strong>cognita on cowpea. Global Journal of Pure and Applied Sciences 2 (1): 9–15.Patel, P.N. 1985. Fungal, bacterial and viral diseases of cowpea <strong>in</strong> the USA. Pages 205–213 <strong>in</strong>Cowpea <strong>research</strong>, production and utilization, edited by S.R. S<strong>in</strong>gh and K.O. Rachie. John Wileyand Sons, Chichester, UK.Patel, P.N. and J.K. J<strong>in</strong>dal. 1982. Dist<strong>in</strong>guish<strong>in</strong>g reactions of the bacterial blight and pustule organismsof cowpea on pods of Phaseolus vulgaris. Zeitschrift fur Pflanzenkrankheiten and Pflanzenschutz89(7): 406–409.119

Cowpea <strong>in</strong>tegrated pest managementPaz, C.D, A.A. Lima, G. Pio-Ribeiro, F.M. Assis Filho, G.P. Andrade, and M.F.B. Goncalves. 1999.Purification of an isolate of cowpea severe mosaic obta<strong>in</strong>ed <strong>in</strong> Pernambuco, production of antiserumand determ<strong>in</strong>ation of sources of resistance <strong>in</strong> cowpea. Summa Phytopathologica 25 (4):285.Premala, J., A.A. Brunt, and P. Jeyanandarajah. 1996. Blackeye cowpea mosaic potyvirus, the causeof a severe disease of vegetable cowpea (Vigna unguiculata ssp. sequipedalis) cv. Polonmae <strong>in</strong>Sri Lanka. Tropical Science 36(3): 129–137.Puruthi, I.J., R.J. Ja<strong>in</strong>, and D.C. Gupta. 1995. Relative susceptibility of a few vegetable crops totwo species of root knot nematodes. Haryana Journal of Agricultural Science 24(1): 76–78.Rahman, M.L., M.S. Haque, A. Muqit, K.B. Alam, and S. Ali. 1994. Response of Sclerotum rolfsiito different fungicides. Bangladesh Journal of Plant pathology 10(1–2): 35–36.Rakesh, S., M.K. Bhatnagar, and R. Shah. 1994a. Influence of <strong>in</strong>oculum concentration and multiplicationof Xanthomonas campestris pv. vignicola on cowpea. Legume Research 17(3–4):154–156.Rakesh, S., M.K. Bhatnagar, and R. Shah. 1994b. Survival of Xanthomonas campestris pv. vignicolacaus<strong>in</strong>g bacterial blight of cowpea. Indian Journal of Mycology and Plant Pathology 24(3):206–208.Rakesh, S., M.K. Bhatnagar, and R. Shah. 1995. Effect of plant age and <strong>in</strong>oculation methods onbacterial blight development <strong>in</strong> cowpea. Indian Journal of Mycology and Plant Pathology 25(3):314–315.Ram, S., S. Hari, D.S. Dodan, R. S<strong>in</strong>gh, and H. S<strong>in</strong>gh. 1995. Sensitivity of Rhizoctonia solaniisolates caus<strong>in</strong>g seedl<strong>in</strong>g mortality of mung to different fungicides. Plant Disease Research 10(1):41–43.Ramadose, S. 1994. Effect of fungicides and <strong>in</strong>secticides on the growth and sclerotic production ofMacrophom<strong>in</strong>a phaseol<strong>in</strong>a (Tassi ) Goid. Madras Agricultural Journal 81(1): 21–23.Rangaiah, S. 1997. Inheritance of resistance to Uromyces phaseolus <strong>in</strong> Vigna unguiculata (L.) Walp.Crop Improvement 24(2): 251–252.Rao, A.L.N. 1997. Molecular studies on bromovirus capsid prote<strong>in</strong>. III. Analysis of cell-to-cellmovement competence of coat prote<strong>in</strong> defective variants of cowpea chlorotic mottle virus. Virology(New York) 232(2): 385–395.Rao, G.M.V.P. and S. Ganguly. 1996. Host preference of six geographical isolates of ref<strong>in</strong>er nematode,Rotylenchulus reniformis. Indian Journal of Nematology 20(1): 19–22.Rathore, B.S. 1995. Effect of granular nematicides aga<strong>in</strong>st reniform nematode, Rotylenchulusreniformis on cowpea. Indian Journal of Mycology and Plant Pathology 25(3): 309–310.Rathore, B.S. and B.S. Yadav. 1996. Effect of chemical seed soak<strong>in</strong>g on plant growth and reproductionof Rotylenchulus reniformis <strong>in</strong> cowpea. Indian Journal of Mycology and Plant Pathology26(3): 281–283.Ratnoo, R.S., K.L. Ja<strong>in</strong>, and M.K. Bhatnagar. 1997. Effect of atmospheric temperature on thedevelopment of ashy stem blight of cowpea. Journal of Mycology and Plant Pathology 27(1):90–91.Reeves, J.C. 1997. Potentially important seedborne pathogens of economic crops <strong>in</strong> Northeast Asia.Pages 73–79 <strong>in</strong> Seed health test<strong>in</strong>g, progress towards the twenty-first century, edited by W.S. Wuand J.D. Hutch<strong>in</strong>s. CAB International, Wall<strong>in</strong>gford, UK.Reiss, G.C. and J.A. Bailey. 1998. Striga gesnerioides parasitiz<strong>in</strong>g cowpea: development of <strong>in</strong>fectionstructures and mechanisms of penetration. Annals of Botany 81(30): 431.Renato, C.P., A. Higuera, and A.M.P. Casassa. 1995. Response of some cowpea accessions toMeloidogyne spp. Revista de la Facultad de Agronomia, Universidad del Zulia 12(4): 485–490.Roberts, P.A., J.D. Ehlers. A.E. Hall, and W.C. Matthews. 1997. Characterization of new resistanceto root knot nematodes <strong>in</strong> cowpea. Pages 207–214 <strong>in</strong> Advances <strong>in</strong> cowpea <strong>research</strong>, edited byB.B. S<strong>in</strong>gh, D.R. Mohan Raj, K.E. Dashiell, and L.E.N. Jackai. Copublication of International120

<strong>Recent</strong> <strong>advances</strong> <strong>in</strong> <strong>research</strong> on cowpea diseasesInstitute of Tropical Agriculture (IITA) and Japan International Research Center for AgriculturalScience (JIRCAS). IITA, Ibadan, Nigeria.Roberts, P.A., C.A. Frate, W.C. Matthews, and P.P. Osterili. 1995. Interactions of virulent Meloidogyne<strong>in</strong>cognita and Fusarium wilt on resistant cowpea genotypes. Phytopathology 85(10): 1288–1295.Roberts, P.A., W.C. Matthews, and J.D. Ehlers. 1996. New resistance to virulent root-knot nematodesl<strong>in</strong>ked to the RK locus of cowpea. Crop Science 36(4): 889–894.Rodriguez, I., M.G. Rodriguez, L. Sanchez, and A. Iglesias. 1996. Expression of resistance toMeloidogyne <strong>in</strong>cognita <strong>in</strong> cowpea cultivars (Vigna unguiculata). Revista de Protection Vegetal11(1): 63–65.Rodriguez, V.J.L.B., M. Menezes, R.S.B. Coelho, and P. Miranda. 1997. Identification of resistancesources on genotypes of cowpea (Vigna unguiculata) to Macrophom<strong>in</strong>a phaseol<strong>in</strong>a (Tass.) Goid.under greenhouse conditions. Summa Phytopathologica 23(2): 170–172.Roy, K.W. and S. Ratnayake. 1997. First report of Phomopsis longicolla <strong>in</strong>fection of cowpea podsand seeds <strong>in</strong> Mississippi. Plant Disease 81(6): 693.Ryerson, D.E. and M.C. Heath. 1996. Inheritance of resistance to the cowpea rust fungus <strong>in</strong> cowpeacultivar Calico Growder. Canadian Journal of Plant Pathology 18(4): 384–391.Santhi, A., S. Rajeswari, and R. Sundarababu. 1995. Effect of three species of VAM viz Glomusfasciculatus, G. versiforme, G. etunicatus and root knot nematode Meloidogyne <strong>in</strong>cognita oncowpea grow<strong>in</strong>g <strong>in</strong> different types of soil. International Journal of Tropical Plant Diseases 13(1):63–68.Santhi, A. and R. Sundarababu. 1995. Effect of phosphorus on the <strong>in</strong>teraction of vesicular arbuscularmycorrhizal fungi with Meloidogyne <strong>in</strong>cognita on cowpea. Nematologia Mediterranea 23(2):263–265.Santos, A.A., M.A.W. Qu<strong>in</strong>dere, and M.B. Melo. 1997. Evaluation of cowpea genotypes for resistanceto cowpea smut (Entyloma vignae). Fitopatologia Brasileira 22(1): 77–78.Sarmah, B. and A.K. S<strong>in</strong>ha. 1995. Pathogenicity of Meloidogyne <strong>in</strong>cognita on cowpea. Plant Health1: 12–14.Schneider, W.L., A.E. Greene, and R.F. Allison. 1997. The carboxy term<strong>in</strong>al two-thirds of the cowpeachlorotic mottle bromovirus capsid prote<strong>in</strong> is <strong>in</strong>capable of virion formation yet supports systemicmovement. Journal of Virology 71(6): 4862–4865.Sharma, S.B., T.J. Rego, M. Mchiudd<strong>in</strong>, and V.N. Rao. 1996. Regulation of population densities ofHeterodera cajani and other plant-parasitic nematodes by crop rotations on vertisols <strong>in</strong> semi-aridtropical production systems <strong>in</strong> India. Journal of Nematology 28(2): 244–251.Shoy<strong>in</strong>ka, S.A., R.F. Bozarth, J. Rees, and H.W. Rossel. 1978. Cowpea mottle virus: a seedbornevirus with dist<strong>in</strong>ctive properties <strong>in</strong>fect<strong>in</strong>g cowpea <strong>in</strong> Nigeria. Phytopathology 68: 693–699.Sikirou, R. 1999. Epidemiological <strong>in</strong>vestigations and development of <strong>in</strong>tegrated control methodsof bacterial blight of cowpea caused by Xanthomonas campestris pv. vignicola. PhD thesis.University of Gott<strong>in</strong>gen, Germany. 218 pp.Sikirou, R.K., K. Wydra, and K. Rudolph. 1998a. Inoculum source of Xanthomonas campestris pv.vignicola, <strong>in</strong>citant of cowpea bacterial blight and pustule, and identification of other hosts besidesVigna unguiculata. International Congress of Plant Pathology, 9–16 August 1998, Ed<strong>in</strong>burgh,UK. Abstract 6.67.Sikirou, R.K., K. Wydra, and K. Rudolph 1998b. Survival of Xanthomonas campestris pv. vignicola,<strong>in</strong>citant of cowpea bacterial blight and pustule on weeds and <strong>in</strong> soil and identification of otherhosts besides Vigna unguiculata. Mitteilung Biologische Bundesanstalt 357: 223.S<strong>in</strong>gh, B.B. and A.M. Emechebe. 1997. Advances <strong>in</strong> <strong>research</strong> on cowpea Striga and Alectra. Pages215–223 <strong>in</strong> Advances <strong>in</strong> cowpea <strong>research</strong>, edited by B.B. S<strong>in</strong>gh, D.R. Mohan Raj, K.E. Dashiell,and L.E.N. Jackai. Copublication of International Institute of Tropical Agriculture (IITA) andJapan International Research Center for Agricultural Science (JIRCAS). IITA, Ibadan, Nigeria.Sivakumara, K., B.C. Fouler, and D.L. Hacker. 1998. Identification of viral genes required for cellto-cellmovement of southern bean mosaic virus. Virology (New York) 252(2): 376.121

Cowpea <strong>in</strong>tegrated pest managementSmith, J.E., L. Christen, and T.A.S. Avel<strong>in</strong>g. 1999a. Infection process of Colletotrichum dematiumon cowpea stems. Mycological Research 103(2): 230–234.Smith, S.N., D.M. Helms, and S.R. Temple. 1999b. The distribution of Fusarium wilt of blackeyedcowpeas with<strong>in</strong> California caused by Fusarium oxysporum f.sp. tracheiphilum race 4. PlantDisease 83(7): 694.Stofella, P.J., R.C. Bullock, and R.M. Sonoda. 1990. Influence of pesticide spray schedules ongrowth and yields of cowpeas. Proceed<strong>in</strong>gs of Inter-American Society for Tropical Horticulture34: 83–87.Subramaniyan, S., A.K. Faziullah, G. Rajendran, and S. Vadivelu. 1997. Reaction of some mung,cowpea, lablab and tomato genotypes to the reniform and root knot nematodes. Indian Journalof Nematology 27(1): 130–131.Sunder, S., S.K. Sharma, A.S. Taya, and O.P. Sheoran. 1996. Effect of age and quality of <strong>in</strong>oculum,temperature and pH of substrate on the pathogenic behaviour of Rhizoctoria solani. Plant DiseaseResearch 11(1): 107–110.Thammaiah, N. and A.N.A. Khan. 1995a. Effect of seed treatment on Xanthomonas campestris pv.vignicola causal agent of bacterial blight of cowpea. Advances <strong>in</strong> Agricultural Research <strong>in</strong> India4: 93–102.Thammaiah, N. and A.N.A. Khan. 1995b. Studies on control of Xanthomonas campestris pv. vignicola(Burkh.) dye <strong>in</strong> cowpea seeds by hot water treatment. Advances <strong>in</strong> Agricultural Research<strong>in</strong> India 3: 194–198.Thammaiah, N., A.N.A. Khan, and E. John. 1995. Effects of extracts of Adhatoda zeylanica onXanthomonas campestris pv. vignicola caus<strong>in</strong>g bacterial blight of cowpea. Advances <strong>in</strong> AgriculturalResearch <strong>in</strong> India 4: 109–117.Thottappilly, G., O.P. Sehgal, and H.W. Rossel. 1993. Characteristics of a cowpea chlorotic mottlevirus isolate from Nigeria. Plant Disease 77: 60–63.Toure, M, A. Oliver, B.R. Ntare, J.A. Lane, and C.A. Pierre. 1998. Reaction of cowpea (Vignaunguiculata) cultivars to Striga gesnerioides races from Mali and Niger. Canadian Journal ofPlant Science 78(3): 477–480.Umaharan, P., R.R. Ariyanayagam, and S.O. Haque. 1997a. Resistance to cowpea severe mosaicvirus, determ<strong>in</strong>ed by three dosage-dependent genes <strong>in</strong> Vigna unguiculata (L.) Walp. Euphytica95(1): 49–95.Umaharan, P., R.R. Ariyanayagam, and S.O. Haque. 1997b. Identification of resistance to cowpeasevere mosaic virus (Tr<strong>in</strong>idad isolate) <strong>in</strong> cowpea (Vigna unguiculata [L.] Walp.). Tropical Agriculture74(4): 324–328.Ushamal<strong>in</strong>i, C., K. Rajappan, and K. Gangadharan. 1997a. Inhibition of Macrophom<strong>in</strong>a phaseol<strong>in</strong>aand Fusarium oxysporum f.sp. tracheiphilum by antagonists under <strong>in</strong> vitro conditions. PlantDisease Research 12(2): 167–170.Ushamal<strong>in</strong>i, C.K., Rajappan, and K. Gangadharan. 1997b. Control of Macrophom<strong>in</strong>a phaseol<strong>in</strong>aand Fusarium oxysporum f.sp. tracheiphilum by antagonists under field conditions. Plant DiseaseResearch 12(2): 122–129.Ushamal<strong>in</strong>i, C., K. Rajappan, and K. Gangadharan. 1997c. Suppression of charcoal rot and wiltpathogens of cowpea by botanicals. Plant Disease Research 12(2): 113–117.Vale, C.C. and J.A. Lima. 1995. The <strong>in</strong>heritance of immunity <strong>in</strong> Vigna unguiculata Macaibo tocowpea severe mosaic virus. Fitopatologia Brasileira 20(1): 30–32.Vauter<strong>in</strong>, L., B. Hoste, K. Kersters, and J. Sw<strong>in</strong>gs. 1995. Reclassification of Xanthomonas. InternationalJournal of Systematic Bacteriology 45: 472–489.Vauter<strong>in</strong>, L., J. Rademaker, and J. Sw<strong>in</strong>gs. 2000. Synopsis on the taxonomy of the genus Xanthomonas.Phytopathology 90(7): 677–682.Verdier, V., K. Assigbetse, G. Khatri-Chhetri, K. Wydra, K. Rudolph, and J.P. Geiger. 1998.Molecular characterisation of the <strong>in</strong>citant of cowpea bacterial blight and pustule, Xanthomonascampestris pv. vignicola. European Journal of Plant pathology 104: 595–602.122

<strong>Recent</strong> <strong>advances</strong> <strong>in</strong> <strong>research</strong> on cowpea diseasesVerma, J.S. and S.N. Mishra. 1989. Evaluation of improved l<strong>in</strong>es from IITA <strong>in</strong> humid-subtropicalIndia. Tropical Gra<strong>in</strong> Legume Bullet<strong>in</strong> 36: 38–39.Verver, J., J. Well<strong>in</strong>k, J. van Lent, K. Gop<strong>in</strong>ath, and A. van Kammen. 1998. Studies on the movementof cowpea mosaic virus us<strong>in</strong>g the jellyfish green fluorescent prote<strong>in</strong>. Virology (New York)242(1): 22–27.Wikoff, W.R., J.O. Tsai-Chao, T.S. Baker, J.E. Johnson, and G.J. Wang. 1997. The structure ofcucumber mosaic virus, cryoelectron microscopy, x-ray crystallography, and sequence analysis.Virology (New York) 232(1): 91–97.Williams, R.J. 1975. Diseases of cowpea (Vigna unguiculata [L.] Walp.) <strong>in</strong> Nigeria. PANS 21(3):253–267.Xu, H.X. and M.C. Heath. 1998. Role of calcium <strong>in</strong> signal transduction dur<strong>in</strong>g the hypersensitiveresponse caused by basidiospore derived <strong>in</strong>fection of the cowpea rust fungus. Plant Cell 10(4):585–597.Youssef, M.M.A. and M.S. Ali. 1998. Management of Meloidogyne <strong>in</strong>cognita <strong>in</strong>fect<strong>in</strong>g cowpea byus<strong>in</strong>g native blue green algae. Anzeiger fur Schadl<strong>in</strong>gskunde Pflanzenschutz, Umweltschutz 71:15.Youssef, M.M.A. and W.A. Am<strong>in</strong>. 1997. Effect of soil amendment <strong>in</strong> the control of Meloidogynejavanica and Rotylechulus reniformis <strong>in</strong>fection on cowpea. Pakistan Journal of Nematology 15:55–63.Zeng, Y., Z. Wang, and C. Zhao. 1999. Studies on the techniques for evaluation of resistance ofcowpea seedl<strong>in</strong>gs to rust disease. Journal of South Ch<strong>in</strong>a Agricultural University 20(2): 23–27.123