GENE-ACTION FOR ADULT-PLANT RESISTANCE TO POWDERY MILDEW IN WHEAT

Gene action for adult-plant resistance to powdery mildew was studied u sing generation mean analyses of parents and of F-1, F-2, and backcros s populations derived from a diallel cross of one susceptible and thre e adult-plant resistant wheat cultivars. Joint scaling tests showed th at an additive-dominance model was sufficient to explain the variabili ty in the expression of adult-plant resistance in one cross, while dig enic epistasis was involved in the other five crosses. Additive gene e ffects were predominant; however, dominance was significant in four cr osses, additive X additive interaction was significant in three crosse s, additive X dominance interaction was significant in three crosses, and dominance X dominance interaction was significant in one cross. Th erefore, selection for adult-plant resistance would likely be most eff ective in advanced generations derived from crosses among the adult-pl ant resistant cultivars Redcoat, Houser, and Massey.