Genetic analysis of grain mould resistance in coloured sorghum genotypes

Grain moulds are a major constraint to sorghum production and to adoption o f improved cultivars in many tropical areas. Information on the inheritance of grain mould reaction is required to facilitate breeding of resistant cu ltivars. The genetic control of grain mould reaction was studied in 7 cross es of 2 resistant sorghum genotypes. P-1, P-2, F-1, F-2, BC1 and BC2 famili es of each cross were evaluated under sprinkler irrigation for field grade and threshed grade scores and subjected to generation mean analysis. Freque ncy distributions for grain mould reaction were derived and F-2 and BC1 seg regation ratios were calculated. Grain mould reaction in crosses of coloure d grain sorghum was generally controlled by two or three major genes. Resis tance to grain moulds was dominant. Significant additive gene effects were also found in all cross/season combinations. Significant dominance effects of similar magnitude to additive effects were also observed in five out of ten cross/season combinations. Gene interactions varied according to the pa rents with both resistant and susceptible parents contributing major genes. Choice of parents with complementary resistance genes and mechanisms of re sistance will be critical to the success of resistance breeding.