GENETIC ANALYSIS OF RESISTANCE TO RACE 2F. OF PODOSPHAERA XANTHII IN WILD MELON MATERIAL 'YUNTIAN-930'

‘Yuntian-930’ is a wild melon that is highly resistant to powdery mildew (PM). To determine the inheritance of resistance to powdery mildew (PM), ‘Yuntian-930’ was crossed with another cultivated melon, ‘Hualaishi’, which is susceptible to PM. Inheritance of resistance to Podosphaera xanthii race 2F. in six plant generations (P1, P2, F1, B1, B2, and F2) was studied using the mixed major-gene plus polygene inheritance mode with joint analysis method. Inheritance of resistance in wild melons fitted the model of two pairs of additive-dominance-epitasis major genes plus additive-dominant-epitasis polygene. The additive, dominant, and epistatic effects between the two major genes played an important role in inheritance. The estimated values of heritability of major genes in B1, B2, and F2 were 62.98, 58.58 and 90.89%, and those of polygene heritability were 28.93, 31.47 and 3.22%, respectively. The ratios of the environmental variance to phenotype variance were 5.89-9.94%. Thus, resistance of ‘Yuntian-930’ to PM was controlled not just by two major genes, but was also affected by polygene and the environment. The selection efficiency for a major gene of F2 was highest in the resistance breeding program.