Evaluation of maize hybrids containing different proportion of NC298 tropical germplasm line in their male parents

Abstract

Two main questions in programs introgressing exotic maize germplasm into temperate materials are the choice of available exotic sources to work with, and the proportion of exotic germplasm that should be incorporated into adapted germplasm. The objectives of this study were to compare effects of the different proportions of tropical maize germplasm (via inbred NC298) in hybrids male parent, on grain yield, grain moisture content, cultivars stability performance and genotype-by-environment interaction. Using direct crosses and backcrosses (between NC298, Mo17 and NS796 male lines) five male groups were formed containing 0, 25, 50, 75 and 100 percent of tropical germplasm, respectively (or one half in their corresponding hybrids). Each male parent group was tested with three female inbred-testers that belong to the Reid yellow dent heterotic group. The level of significance between mean values of hybrids containing the different proportion of NC298 line in male parent was estimated by F value using Repeated-Measure Design (RMD). Individual genotype stability over environments for grain yield was determined by regression coefficient (b(i)) and R-2 regression value. Genotype-by-environment interaction for grain yield and grain moisture content was estimated by AMMI (Additive main effects and multiplicative interaction) method. Individual genotypic stability did not restrict the choice of desirable genotypes between and/or within groups containing different proportion of tropical germplasm, and no association between genotype stability and the proportion of tropical germplasm could be defined. The NC298 tropical germplasm inbred line of maize, could be incorporated into temperate breeding material comprising 25% of the foundation population proportion, for both grain yield and grain moisture content.