EVALUATION OF THE ASSUMPTIONS REQUIRED FOR THE GENETIC INTERPRETATION OF DIALLEL EXPERIMENTS IN SELF-POLLINATING CROPS

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Abstract
Simulation of two-locus genetic models was used to investigate the effects of gene frequency, non-random association of genes, and epistasis on the interpretation of diallel experiments in self-pollinating crops. It was demonstrated that general combining ability includes effects due to additive, epistatic, and, when gene frequencies are not equal to 0.5, dominance gene action. Similarly, when gene frequencies do not equal 0.5, average heterosis depends upon additive × dominance interaction as well as dominance and dominance × dominance interaction. Negative associations between genes greatly inflate the apparent amount of specific combining ability. These findings cast serious doubt on the utility of diallel analysis for studying the genetics of self-pollinating crops.