Relationships between heterosis, genetic distances and specific combining ability among CIMMYT and Zimbabwe developed maize inbred lines under stress and optimal conditions

Abstract

Genetic characterisation of breeding lines is of great importance as it enables breeders to maximise heterosis in hybrid combinations as well as in the breeding material. In this study 10 Department of Research and Specialist Services and 13 Centre for the Improvement of Maize and Wheat inbred lines were crossed using a North Carolina II mating scheme and were genotyped using 1,129 single nucleotide polymorphic (SNP) markers. The resultant 72 single cross hybrids together with eight different local checks were evaluated across seven locations in Zimbabwe in the 2009/2010 and 2010/2011 seasons. SNP markers yielded a total of 2,258 alleles and a moderate genetic diversity and polymorphic information content of 0.32 and 0.258, respectively. Clustering of lines did not relate to available pedigree information. Significant positive correlations were recorded for specific combining ability with mid parent heterosis (MPH), high parent heterosis (HPH) and per se performance of hybrids. However, correlations of genetic distances with heterosis under drought conditions were too low to be of predictive value. The HPH and MPH also showed significant positive associations along with high coefficients of determination with per se performance of hybrids, especially under drought.