Evidence suggests that Mycosphaerella pinodes infection of Pisum sativum is inherited as a quantitative trait

Abstract

Before likely sources of resistance in pea to Mycosphaerella pinodes can be exploited in a breeding program, the inheritance of genetic mechanisms governing the variation in resistance need to be understood. Disease responses were first examined in a diallel cross of nine Pisum sativum genotypes. An analysis of variance of parental and F₁ data detected significant additive and dominance variation but no reciprocal effects. Gene interactions were not significant in leaves with the exception of the line JI 252 and there was no association detected between the frequencies of dominant or recessive alleles and parental disease response. In stems, the slope of the regression line of the covariance if array members with their non recurrent parent on the variance of an array was significantly different from one and the additive-dominance model was therefore rejected. The non-significance of interactions among genes determining disease response in leaves was supported by the triple test cross analyses. These analyses showed that the narrow-sense heritability of disease response was higher in crosses involving SA 1160 than in the cross Wirrega × Austrian Winter. These crosses are likely to generate inbred lines more resistant to M. pinodes infection than either parent.