Vol.12_No.2 - Pesticide Alternatives Lab - Michigan State University

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Spring 2003 Resistant Pest Management Newsletter Vol. 12, No.2need for educating the farmers about the pests,insecticides, and their uses to avoid indiscriminateusage and to prevent a chain of problems that effectnature and human health.REFERENCES:1. Kranthi KR , Jadhav DR, Wanjari RR, Shakir Ali S Russel D.Carbomate and organophosphate resistance in cotton pests in India,1995 to 1999. Bull. Ent. Res., 2001; 91:37-46.2. Patil B.V, Lingappa S, Srinivasa A.G, Bheemanna M. Integrated pestManagement Strategies for Cotton. Paper presented at XXinternational congress of Entomologyheld at Firenze, Italy from 25-31, August 1996.3. Kranthi KR, Armes NJ, Nagarjun GV, Rao RS, Sundaramurthy VT.Seasonal dynamics of metabolic mechanisms mediating pyrethroidresisitance in Helicoverpa armigera in central India. Pestic. Sci.,1997;50:91-98.4. Lingappa S, Panchabhavi KS, Hugar PS. Managament of cottnbollworms with special reference to Heliothis in Karnataka.Petology, 1993;17(9):20-25.ACKNOWLEDGEMENT: The financial assistance in theform of a project by Dept. of Biotechnology (DBT),Govt. of India is gratefully acknowledged by Dr. B.Fakrudin. We are also grateful to all the scientists at allthe sampling locations in South India who helped invarious ways during our visit.5. Armes NJ, Jadhav DR, Bond GS, King ABS. Insecticide resisitance inHelicoverpa armigera in South India. Petic. Sci. 1992:34:355-364.6. Rakila A, Padmanabhan NR.. Knowledge and factors influencingpesticide use and frequency of plant protection measures.Pestology,1995;19: 9-127. Jadhav DR, Armes NJ. Comparitive status of insecticde resisitance inHelicoverpa and Heliothis species (Lepidoptera: Noctuidae) ofSouth India. Bull. Ent. Res. 1996; 86:525-531.B. Fakrudin, B. V. Patil, P. R. Badari Prasad, & S. H.PrakashDepartment of BiotechnologyUniversity of Agricultural SciencesDharwadIndiaRecent Advances in Host Plant Resistance to Whiteflies in CassavaINTRODUCTION Whiteflies are considered one of theworld’s major agricultural pest groups, attacking awide range of plant hosts and causing considerablecrop loss. There are nearly 1200 whitefly species witha host range that includes legumes, vegetables, fruittrees, ornamentals, and root crops. As direct feedingpests and virus vectors, whiteflies cause major damagein agroecosystems based on cassava (Euphorbiaceae;Manihot esculenta Crantz) in the Americas, Africa, andto a lesser extent Asia. The most damaging species oncassava in northern South America is Aleurotrachelussocialis. Typical damage symptoms include curling ofapical leaves, yellowing and necrosis of basal leaves,and plant retardation (Fig. 1). Adult whiteflies are mostfrequently observed on the underside of apical leaveswhere they feed on plant fluids and oviposit. The"honeydew" excreted is a substrate for a sooty-moldfungus that interferes with photosynthesis (Fig. 1C).The combination of direct feeding and impairedphotosynthetic rate reduces root yield by 4% to 79%depending on the duration of attack (Bellotti, 2002).More than 5,000 cassava genotypes have been38
Spring 2003 Resistant Pest Management Newsletter Vol. 12, No.2evaluated at CIAT and CORPOICA for whiteflyresistance. At present, the major source of hostresistance in cassava is the genotype MEcu-72 (Bellottiand Arias, 2001) (Fig. 1D). When feeding on MEcu-72A. socialis had less oviposition, longer developmentperiods, reduced size, and higher mortality than whenfeeding on the susceptible genotype (Fig. 2). Due to theimportance of whiteflies as a pest and virus vector, it isimportant to understand the nature of genes that conferresistance in the resistant genotype, MEcu-72. To studythe genetics of this resistance, a cross was madebetween MEcu-72 (resistance genotype) x MCol-2246(a very susceptible genotype), to evaluate F1segregation, using molecular markers. This willaccelerate the selection of whitefly resistant germplasmand isolate resistant genes.MATERIALS and METHODSPlant Material: For the present work we have used thecross MEcu-72 (as the resistant parent) x MCol-2246(as the susceptible parent). A total F1 offspring of 286genotypes (family CM8996) was produced from thiscross. These materials were sowed and evaluated in thefield during May 2001, March and August 2002 at twodifferent locations: Espinal-Tolima, Colombia(CORPOICA-NATAIMA) at 350 m.a.s.l. andSantander de Quilichao, Cauca, Colombia, at 990m.a.s.l. With this evaluation we will identify genesegregation in the offspring and we will be able toselect the resistant and susceptible materials. Theevaluation was performed in the field using populationand damage scales ranging between 1-6, where 1 is anabsence of damage and population and 6 is highpopulation and damage(curling, chlorosis, sooty moldfungus, etc.) (Table 1). Threeevaluations were performed in2002 using the highest damageand population data forinformation processing.genome equivalents. The whitefly resistance will betarget for map-based cloning using the BAC librariesas tools. We are using silver staining to visualize theallelic segregation of the markers.RESULTSField Evaluation: The whitefly resistant variety CG489-31 (Fig. 2), a progeny from the MEcu 72 x MBra12 cross, has been released to cassava farmers byCORPOICA, Colombia under the name Nataima-31(Fig. 3).Initial field evaluations showed that thesematerials (family CM 8996) had low levels of the pest,because test plants (materials very susceptible to A.socialis) did not present high levels of damage andpopulations (scale of 4 to 6 Table 1). The harvestevaluation showed that the root yield was between 4.5and 86.5 ton/ha, and many materials presenteddesirable characteristics (high percentage of dry matter,palatability, etc.). Currently, the family is under asecond sowing cycle at the same locality from Tolima,and high pressure exerted by the pest has been detectedsince test materials have high degrees of damage (from4 to 5).Preliminary evaluations have demonstrated thatsome materials from the family present low levels ofdamage and population (up to 2) (Fig. 4 and 5).Molecular Analysis: Both parents MEcu-72 and MCol-2246 were evaluated with 343 cassava SSR markers(Mba et al, 2001) including 156 cDNA SSRsdeveloped (Mba et al, by submitted). Approximately155 of the SSRs were polymorphic in the parentals andMolecular Analysis: We areusing Simple Sequences Repeat(SSR) to find markersassociated with resistance formapping the resistant gene(s).As part of a collaborativeproject with ClemsonUniversity funded by USAID aBAC library for cassava usingthe clone MEcu 72 wasconstructed. The librarycontains 73,728 clones with anaverage insert size of 93 kb.Based on a genome size of 760Mb, library coverage isapproximately 10 haploid39
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