Genetic studies on resistance to powdery mildew disease in snake melon (cucumis melo l. var flexousus)

Three experiments (I, II and III) were conducted for two successive seasons 2006/2007 and 2007/2008 at Gezira Research Station Farm, Agricultural Research Corporation, Wad Medani Sudan, to screen for resistance/tolerance to powdery mildew disease in Snake melon: to identify the common powdery mildew species in Central Sudan using differential lines and to determine the mode of inheritance of powdery mildew resistance in snake cucumbcr. Augmented design with five replications was used in experiment I and Randomized complete block design (RCBD) with three replications was used in expcriments II and III. Local cultivars and differential lines were used to estimate inheritance and genetic components of resistance following identification of resistant lines and resistance was transferred to susceptible background or further genetic studies. Results of experiment I were homogenous and not n single plant from any accession or susceptible check had escaped infection. This indicated that natural infection conditions were adequate for screening snake melons using severity scale and incidence (%). Results of experiment II indicated that the differential lines and the two checks were divided in to two groups based on reaction to powdery mildew disease (incidence and severity). The resistant group included MR 1, PMR5, PI 414723 and PI 124112, while the susceptible group included WMR 29, PMR 45, Vedratantais, Edisto47, Silka, Shendi and Nantais oblong. Further more, our results indicated the presence of tow, powdery mildew species, Sphacrotheca fuliginea and Erysiphe cichoracearum. Quantitative analysis results of experiment III indicated that dominant genetic effect had the major contribution to the genotypic variation and that the dominance was complete in the direction of susceptibility. Estimates of number of effective resistance factors indicated the presence of one or three factors conditioning the resistance. Chi square test revealed that resistance for powdery mildew in the differential lines was controlled by one or three linked genes, which was dominant in two crosses, Silka x PI 124112 and Silka x MR 1 and partially dominant in the third cross Silka x P1 414723