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Evaluation of the Cross Eskandarany x Whitaker for Powdery Mildew Resistance (PMR), Zucchini Yellow Mosaic Virus Resistance (ZYMR) and Some Yield Characters E.A Ahmed, H.S. Ibn oaf, and A.E EL Jack Faculty of Agriculture, University of Gezira, Sudan M.E. Abdelmohsin Faculty of Natural Resources, University of Kordofan, Sudan Introduction: Cucurbits play a significant role in human nutrition, especially in tropical countries where their consumption is high. Cucurbit crops constitute a major portion of vegetables and are grown in different regions of the Sudan. Squash is a promising export crop which can be readily produced at a low cost during the winter season of Sudan. Zucchini yellow mosaic virus (ZYMV) and powdery mildew (PM) are major diseases in Sudan, causing significant yield losses (1,2). Summer production of squash resulted in low yield caused by failure of fruit development (5). The popular commercial cultivar of squash in Sudan is ‘Eskandarany’ which is susceptible to ZYMV and PM . The cultivar Whitaker is a summer squash released in 1998 at Cornell University (USA). Whitaker is resistant to four important diseases: ZYMV, papaya ring spot virus (PRSV), cucumber mosaic virus and PM (10). Two aggressive isolates of ZYMV, Su19 and Su4, were reported in Sudan (4). The isolate Su19 is an aggressive isolate widely distributed in central Sudan where the field test was done. It incites typical yellow mosaic, deep foliar serration, blisters, deformation and plant stunting on the susceptible cv. Eskandarany. Powdery mildew caused by Sphaerotheca fuliginea (Schlecht. Ex Fr. Pol), race 0, 1 and 2 were reported (3), with seasonality of race prevalence. Resistance to PM was reported in wild Cucurbita lundelliana (12). This resistance was found to be conferred by a single dominant gene. Another wild squash, C. martinezii, was reported to be resistant to PM and this resistance was transferred to C. pepo (7). A single incompletely dominant gene zym plus some modifiers has been reported to confer resistance to ZYMV (8). Cucurbit Genetics Cooperative Report 24:77-79 (2001) The objectives of this study were to determine (1) the inheritance of resistance to PM and ZYMV, and (2) the yield potential of the parents in cross combination. Materials and Methods: Cultivar Eskandarany was selfed for four generations to ensure homozygosity. Six generations P1 (Eskandarany), P2(Whitaker), F1, F2, BCP1, BCP2 were generated at University of Gezira farm. The six generations were evaluated during the winter season of 2000/2001. The experimental design used was a randomized complete block design with three replicates . Evaluation of powdery mildew was done under natural conditions of infection. A scale of 1 to 9 was used (2), where 1 = stem: fungal growth with luxuriant sporulation; leaf: completely covered with fungal growth with luxuriant sporulation; 9 = stem and leaf free of fungal growth. Evaluation was done once at the end of the season and when the susceptible parent (P1) was completely infected. Melon genotypes obtained from INRA, France were used to identify the PM causal agent (Table 1). Evaluation for ZYMV was done under field conditions in season 1998/99 in Sudan. A scale of 1 to 9 was used, where 1=the plant is severely infected and is showing shoestringing symptoms, 9= no apparent symptoms of the virus. Mechanical inoculation with ZYMV-Su19 was done in the green house and ELISA testing at INRA, Montfavet, France. Three yield characters were measured: 1. number of days to flowering 2. ovary length at flowering (cm). 3. number of days from flowering to harvest (marketable size). 77
Table 1: Observed reaction of melon genotypes to powdery mildew. Iran H Nantai s oblong PMR 45 WMR 29 MR1 PMR5 PI 12411 2 PI 41472 3 S S R R R R R R R Table 2. Inheritance of powdery mildew resistance in cv. Whitaker (Cucurbita pepo L.). Edisto Generation No of Z R S Expected ! plants Ratio 2 P P1 35 0 35 0:1 P2 16 16 0 1:0 F1 38 38 0 1:0 F2 335 272 62 3:1 1.674> 99% BCP1 36 17 19 1:1 0.014> 99% BCP2 35 35 0 1:0 Z R: resistant, S: susceptible Table 3. Generation means of ovary length, days to flowering and days to harvest marketable fruits. Generation Ovary length(cm) Days to flowering Days to harvest z P1 5.6±0.13 55.5±0.79 6.2±0.13 P 2 7.6±0.23 56.2±1.16 3.4±0.2 F 1 8.3±0.31 45.8±0.9 5.1±0.2 F 2 7.8±0.08 52.1±0.46 4.7±0.07 BCP 1 6.8±0.2 53±1.09 4.8±0.2 BCP 2 8.2±0.21 49.9±1.21 4.8±0.24 P 1: Eskandarany, P 2: Whitaker For generation mean analysis, six parameter model (6) was used (m=mean, d=additive effect, h=dominance effect, i=additive x additive, j=additive x dominance, l= dominance x dominance). Narrow sense heritability (h 2 N) was estimated according to the partition of variance (11). Results and Discussion: The Chi-square analysis revealed a good fit for a single completely dominant gene hypothesis for resistance to powdery mildew (Table 2) . According to the observed reaction of the differential genotypes race 1 of Sphaerotheca fuliginea is prevailing (Table 1). Nantais oblong is known to be resistant to Erysiphe Cichoracearum and Cucurbit Genetics Cooperative Report 24:77-79 (2001) race 0 of S. fuliginea whereas PMR45 is resistant to race 1 and susceptible to race 2 of S. fuliginea. The cv. Whitaker displayed a high level of resistance to zucchini yellow mosaic virus (ZYMR=8) under natural infection conditions. Plants showed very light mosaic producing fruits with normal shape, size and color. The F1 (Eskandarany x Whitaker) showed an intermediate level of resistance (ZYMR=5). The plants displayed a high level of mottling on leaves but they were vigorous and produced marketable fruits. Upon inoculation with the isolate Su 19 the cv. Whitaker displayed clear mosaic. The ELISA test confirmed the presence of the virus, but the virus 78
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Cucurbit Genetics Cooperative Coope
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The Cucurbit Genetics Cooperative (
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Cucumber Inbred Line USDA 6632E Jac
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Multiple Shoot Induction from the S
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Table 2. Shoot induction efficiency
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Figure 1. The viability of Cucumis
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Gynogenesis in a Dihaploid Line of
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Resistant Blister Reaction to Powde
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Table 1. Analysis of variance for p
Page 37 and 38: Fusarium Wilt Resistance in Eight I
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Page 45 and 46: Table 1. Percentage of RAPD band pr
Page 47 and 48: Inodorus Primer Casaba Honeydew Cha
Page 49 and 50: Frequency of RAPD Polymorphisms in
Page 51 and 52: BC551 76.6 92.9 38.5 20.5 38.9 42.2
Page 53 and 54: Powdery Mildew: An Emerging Disease
Page 55 and 56: Table 1 (continued).z Cultivar Coun
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Page 65 and 66: Table 1. Progeny test of male steri
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Page 75 and 76: 11. Mozumder, B.K.G, N.E. Caroselli
Page 77 and 78: Table 1. Vine length of watermelon
Page 79 and 80: Survey of Watermelon Trialing Metho
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Page 83 and 84: Variation among tropical pumpkin cu
Page 85 and 86: Table 1. Aggressiveness of powdery
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Page 121 and 122: Gene List 2001 for Cucumber Jiahua
Page 123 and 124: Ar - Anthracnose resistance. One of
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Page 127 and 128: gi - ginkgo. Leaves reduced and dis
Page 129 and 130: Mdh-4 Mdh- 3 Malate dehydrogenase-4
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Page 135 and 136: M16056 Cotyledon cDNA Encoding ribu
Page 137 and 138: (for CsPK2.2) AB001590 Hypocotyl RN
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Caruth, T. F. 1975. A genetic study
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John, C. A. and J. D. Wilson. 1952.
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Ohkawa, J., A. Shinmyo, M. Kanchana
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Shimizu, S., K. Kanazawa, and A. Ka
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Youngner, V. B. 1952. A study of th
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Cucurbit Genetics Cooperative 2001-
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Denlinger, Phil Mt. Olive Pickle Co
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Keita, Sugiyama Kurume Branch, Natl
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germplasm evaluation and conservati
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Sarfatti, Matti Hazera Ltd., Resear
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Alabama Fenny Dane Arkansas Ted Mor
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Covenant and By-Laws of the Cucurbi
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ARTICLE IX. General Prohibitions No
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