Combining ability and heterotic grouping of tropical maize using stiff stalk and non-stiff stalk testers

The allocation of inbred lines into heterotic groups is essential for developing high-yielding and stable hybrids in maize breeding programs. Thus, our objective was to allocate tropical maize inbred lines into heterotic groups based on their testcross performance with two temperate testers, GEMS-0002 (Stiff Stalk heterotic group) and GEMN-0249 (Non-Stiff Stalk heterotic group). For this, 79 tropical maize inbred lines were crossed with these testers, and the testcross hybrids were evaluated across five environments in Minas Gerais, Brazil. The trials were laid out in incomplete block design (augmented block). Variance components and effects of general (GCA) and specific (SCA) combining ability were estimated using mixed model approach. Variance components of GCA and SCA were significant. Among the inbred lines with positive GCA estimates for GY, 13 were allocated to the Stiff Stalk group, 13 to the Non-Stiff Stalk group, and 14 to a third heterotic group, based on their SCA effects with the temperate testers. We concluded that these there heterotic groups of lines can be explored by crossing the best lines from one group with the best lines from opposite groups, and the hybrids should be evaluated across different management conditions in tropical environments.