Estimates of Combining Ability and Heterosis for Yield and Yield Traits in Maize Population (Zea mays L.), under Drought Conditions in the Northern Guinea and Sudan Savanna Zones of Borno State, Niger

Combining ability variances and effects were estimated for grain yield and other agronomic traits in maize (Zea mays L.). Nine parental maize varieties consisted of five IITA open pollinated varieties (OPVs) drought tolerant used as lines and four local varieties used as testers with various level of susceptibility to drought. These materials were crossed in a line x tester mating design during the 2007 cropping season to determine the GCA, SCA effects and the level of heterosis. Parents and crosses were evaluated in Biu and Damboa during the cropping season of 2009. Results from analysis of variance and combining ability showed that there were high and significant level of genetic variability among the parental lines used and their hybrids for almost all the traits study, thus suggesting the possibility for genetic improvement. The study also revealed the significant differences of general combining ability (GCA) effects of parents and that of specific combining ability (SCA) effects of hybrids. The relatively smaller proportion of GCA to SCA ratio indicated the predominance of non-additive genetic effects with respect to most of the traits. That is, estimates of GCA were consistently lower than SCA effects in most of the traits evaluated. This suggests that high performing hybrids such as EVDT-99WSTRC0 x EX-DAMBOA WHITE, TZE-WDTSTRQPMC0 x EX-DAMBOA YELLOW, EVDT-W99STRQPMCO x EX-DAMBOA WHITE, EVDT-W99STRQPMCO x EX-DAMBOA YELLOW and TZECOMP3DTC1 x EX-BIU YELLOW may be used to develop potential varieties. Both additive and non-additive gene effects controlled most traits, but non-additive genetic effect was the more prevalence. These hybrids also revealed high parent heterosis in terms of grain yield. Very high level of higher parent heterosis is considered advantageous for drought tolerance and yield improvement. Hence, yield superiority of some hybrids over the higher parents suggested the possibility of their commercial exploitation. The parents: EVDT-99WSTRC0, TZE-WDTSTRQPMC0, and EX-DAMBOA WHITE were identified as the best general combiners in terms of GCA for days to 50% tasseling, for days to 50% silking, anthesis silking interval, plant height, number of cobs per plot, weight of cobs, dehusked cobs and grain yield. The parents and hybrids which featured prominently with respect to better general and specific combining abilities for maize grain yield and other agronomic traits could have genes that can be introgressed in to other promising lines in further developing high yielding and drought tolerant genotype.