Inheritance of resistance to downy mildew (Pseudoperonospora cubensis) in muskmelon (Cucumis melo). II. Generation means analysis of 5 genitors

Abstract

The contribution of the generation means analysis described by Mather and Jinks to the genetic analysis of resistance to downy mildew caused by Pseudoperonospora cubensis in muskmelon (Cucumis melo L) was exam- ined. Five melon cultivars with high to moderate levels of resistance to P cubensis were crossed with 3 susceptible cul- tivars to develop F 1 , F 2 and back-cross generations. Weighted least-square regression analysis indicated that the majority of the variation could be explained by additive effects (84-99%); epistasis effects are the second-most important effects (explaining at most 8%). Dominance ratio, heritability and number of effective factors could be estimated in the crosses that did not exhibit epistasis. All these genetic parameters showed an important variation among the 15 crosses studied. Analysis of the results led to the proposal of a breeding strategy for the resistance character.