A COMPARISON OF METHODS FOR ANALYZING INHERITANCE DATA FOR RESISTANCE TO RED RASPBERRY POWDERY MILDEW

The simultaneous use of models applicable to discontinuous and continuous variation for analyzing the segregation of powdery mildew resistance in red raspberry progenies gave complementary information. The analysis based on the model for discontinuous variation supported the hypothesis that segregation was controlled by two additive genes for resistance and one epistatic gene for susceptibility. This analysis gives information on the possible genotypes of the parents which facilitates predictions on the proportion of resistant seedlings expected in breeding programs.The analysis based on the model for continuous variation also indicated that inheritance was predominantly additive with significant genetic interactions. However, the estimates of parental contributions to the progenies were more widely based, because allowance was made for the effects of different gene viabilities, of modifying genes and of environmental influences on expression of the disease. Estimates of combining ability obtained from this model facilitate predictions of mean resistance of progenies.The use of each model appeared to provide a more complete assessment of parental resistance contributions than either model used alone.