Genetic analysis of powdery mildew resistance in wild melon material 'Yuntian-930'.

'Yuntian-930'(P1),is a wild melon material which was collected and propagated through many generations and it is high resistant to powdery mildew.To find out inheritance of powdery mildew resistance of this wild material,another cultivated melon material 'Hualaishi'(P2),susceptible to powdery mildew,was used to cross with it.All the plant materials of six generations of P1,P2,F1,B1,B2 and F2 were used to study the inheritance of resistance to powdery mildew by the mixed major-gene plus polygene inheritance mode with joint analysis method of multiple generations in the plastic tunnel.The result showed that the inheritance of powdery mildew resistance of wild melon 'Yuntian-930' fitted two pairs of additive-dominance-epitasis major genes plus additive-dominant-epitasis polygene model(E-0 model).The additive effects of the two major gene were equal,both da and db were estimated as-15.76.The dominance effects of the two major gene(ha and hb) were estimated as 14.98 and 19.87,respectively.The dominance effects of the second major gene was higher than that of the first major gene.In the interacted effect between the two major genes,The epistatic effect of dominant×dominant between two major genes(l=-7.73) was smaller than the others,in which the epistatic effect of additive×additive between two major genes(i),the epistatic effect of additive×dominant between two major genes(jab) and the epistatic effect of dominant×additive between two major genes(jba) were 31.46,-26.86 and-17.07 respectively.In B1,B2 and F2,the heritability of major genes were estimated to be 73.31%,69.15% and 97.61% and the polygene heritability to be 18.83%,25.86% and 0,respectively.The ratios of the environmental variance to phenotype variance were 2.39%～7.86%.Thus,it is suggested that the powdery mildew resistance of 'Yuntian-930' was controlled by two major genes and also affected by more minor-genes and environment,the selection efficiency to major genes of the F2 is the highest in the resistance breeding program.