Gene action determining grain yield and chocolate spot (Botrytis fabae) resistance in faba bean

Production of faba bean (Vicia faba L.) is hampered by chocolate spot disease caused by Botrytis fabae. Studies of the genetics of resistance is vital to devise a viable strategy for faba bean breeding. The present study was carried out with the objective to determine the mode of inheritance and maternal effect for chocolate spot resistance and yield. A 10 × 10 full diallel mating design was used to generate 90 F1 hybrids which were evaluated at three sites in Ethiopia with two replications under natural and with artificial inoculation of the pathogen. There was significant variation for chocolate spot resistance and yield among the genotypes (P ≤ 0.001). The general combining ability (GCA) and specific combining ability (SCA) effects were both highly significant (P ≤ 0.001) for chocolate spot resistance. However, the GCA effect was predominant (84.5 %) suggesting that additive gene effects were more important than non-additive effects and that subsequent selection would be effective to enhance disease resistance. In contrast, the SCA effects were predominant (89.3 %) for grain yield suggesting that non-additive gene action was more important which may provide transgressive segregants. Reciprocal effects were generally negligible (<10 %) for both yield and disease resistance. The line ILB-4726, which combined good disease resistance with high grain yield potential would be recommended for faba bean breeding.