Inheritance of resistance to sesame gall midge in Uganda
Sesame gall midge, caused by Asphondylia sesami Felt, is an important constraint to sesame (Sesamum indicum L.) production in Uganda. Few genotypes have been reported on sesame gall midge, especially hairy genotypes. However, for genetic improvement, there is need to understand the mode of resistance to sesame gall midge in these genotypes. Thirty sesame genotypes were screened for gall midge resistance, under field conditions at Ngetta Zonal Agricultural Research development Institute (ZARDI) in northern Uganda. The spreader row technique was used in order to increase insect pressure on the tested genotypes. The half diallel method 2, model 1 was used to cross 5x5 parents. The result showed that non-additive gene action was important in the inheritance of resistance to sesame gall midge. Cross analysis showed that the GCA x site and SCA x site interactions were significant (P< 0.05), indicating that the additive and non-additive gene actions simultaneously controlled the inheritance for the resistance. The estimate of heritability in narrow sense genetic coefficient of determination (analogue heritable proportion) showed that the resistance was not highly heritable. Estimates of GCA and SCA effects suggest that the parent, Local158, was the best combiner for resistance to gall midge; while the parent AjimoA1-5 was the poorest combiner for the trait. Crosses Local158 x 7029-1-2 and Sesim1 x AjimoA1-5 were the best for the resistance to sesame gall midge. The estimates of genetic effects for resistance to sesame gall midge, showed predominance of additive and additive x additive type of epistasis in the inheritance of the resistance, though dominance also had a role in the cross Sesim1 x 7020-1-2.
Keywords: Asphondylia sesami, combining ability, GCA, Sesamum indicum