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Sudan Journal of Agricultural Research

Evaluation of Watermelon (Citrullus spp.) germplasm for resistance to Watermelon Chlorotic Stunt Virus

Raaed M. Mohamed Elhassan, Sadig K. Omara , Gasim A. Dfalla , Mohamed T. Yousif , Ali E. El-jack.

Abstract:

Watermelon Chlorotic Stunt Virus (WmCSV) is the main viral disease infecting watermelon plants in Sudan. It causes complete yield failure in early infection. Resistance to watermelon chlorotic stunt virus was detected in PI 494529 (Citrullus colocynthis) after screening of 96 entries of watermelon (Citrullus spp.) germplasm. Further comparison of PI 494529 with nine selected entries proved that it differed significantly for resistance to WmCSV. One inbred line of PI 494529 proved to be homozygous resistant when tested in summer 1996. Screening of four commercial cultivars, PI 494529, F1s, F2s and Bc1s revealed that resistance to WmCSV is dominant but it seemed to be not simply inherited and might be affected by minor genes. Further confirmation of field results using agroinfection for testing PI 494529, Crimson sweet, F1 and Bc1 showed that PI 494529 and F1 have low viral DNA content compared to Crimson sweet. Meanwhile, Bc1 plants segregated into two plants with low viral DNA and five plants with a slightly higher viral DNA. The results of this study suggested that PI 494529 was the best source of resistance among tested entries. Moreover, using direct backcrosses for breeding resistant varieties without intervals of selfing may lead to considerable losses in level of resistance.
 

Sudan Journal of Agricultural Research Vol. 12  (2008) PP. 87-94