Interaction of mutant loci opaque-2 and waxy on kernel quality and disease susceptibility in maize.

Abstract

Maize (Zea mays L.) is an important cereal in sub-Saharan Africa with more than 40% of the total production consumed directly as food and at least 50% used as raw material in industry. Nonetheless, maize grain is poor in its nutritional and processing qualities attributed to zeins and high amylose in endosperm. The mutations opaque-2 and waxy double lysine and alter starch properties in maize endosperm respectively. However, opaque-2 and waxy mutants are associated with pleiotropic effects but these, are counteracted by modifier genes in endosperm including possibly the waxy locus. The studies presented in this thesis investigated the interaction of waxy with opaque-2 on kernel quality and related plant agronomic traits. In study I, interactions between opaque-2 and waxy loci on kernel modification and related quality traits in maize endosperm were determined. Study II focused on characterizing opaque-2 and waxy maize inbreds and their F1, F2 and backcross progeny for their starch physicochemical properties. In study III the reaction of waxy and opaque-2 inbreds and their derived F1, F2 and backcross progeny to maize foliar diseases was evaluated. Generation means analysis from study I revealed positive additive gene effects for kernel modification and the three-parameter model was inadequate for tryptophan and kernel modification. Study II, revealed variation for starch physicochemical properties among populations implying selection for important starch attributes can be carried out as early as the F2 generation. Study III revealed all genotypes displayed susceptible reaction to maize foliar diseases and suggests future studies utilize artificial inoculation to ensure disease pressure. Overall, studies presented in this thesis provide insight on the effects of combining waxy with opaque-2 on kernel and agronomic characteristics. Such knowledge would be instrumental in guiding breeding of specialty maize lines high in lysine