Analysis of combining ability and heterotic grouping of maize inbred lines under acid soil conditions, control soil and across environments

A line x tester analysis involving 112 test-cross hybrids and their parents was conducted in 12 environments for different agronomic traits from 2012 to 2014 in the Bimodal Humid Forest Zone of Cameroon. The hybrids were crosses between twenty-five inbred lines and three open-pollinated varieties with four testers. The objectives of the study were to estimate general and specific combining ability effects of the inbred lines and to identify heterotic groups of maize inbred lines under stress conditions, control and across environments. A simple lattice design 12 x 12 was used with two replications. Analysis of variance indicated significant mean squares due to line (GCA) for yield, plant aspect, ear aspect, ear height, plant height and anthesis – silking interval under acid soil conditions. The effect of the tester (GCA) was not significant for yield but line x tester (SCA) showed significant effect for all the traits taken under stress environment. The comparison of GCA sum of squares to SCA sum of squares showed that the contribution of SCA was higher for almost all the traits recorded under acid soil, control and across environments except for ear height in acid soil environments. Most of these traits were predominantly controlled by non-additive gene actions in their expression. SCA explained 68%, 73% and 53% of the total sum of squares among crosses under acid soil, control soil and across environments, for yield. Meaning that yield was mainly controlled by the non-additive genes than the additive gene in the study environments. This confers the advantage of exploiting heterosis to improve grain yield of maize hybrids. Four distinct heterotic groups were identified under acid soil and across environments.