Estimation of Genetic Parameters Controlling Inheritance of Maize Quantitative Traits under Different Plant Densities Using Line × Tester Analysis

Type of gene action, heritability and genetic advance from selection are prerequisites for starting a breeding program for developing plant density tolerant variety of maize. The objective of the present investigation was to estimate general (GCA) and specific (SCA) combining ability variances, type of gene action, heritability and genetic advance from selection for traits related to high density tolerance in maize. A split plot experiment with three replications was carried out; where plant densities were devoted to main plots, namely low (LD), medium (MD) and high (HD) density (47,600 to 71,400 and 95,200 plants/ha, respectively) and sub-plots to genotypes. A line x tester analysis was used. Both GCA and SCA variances were important in the expression of studied traits under all plant densities, but magnitude of δ2SCA was much higher than that of δ2GCA. Estimates of dominance (δ2D) genetic variance were appreciably larger than additive (δ2A) variance estimates for most studied traits under all plant densities, so the breeding method of choice for improving maize plant density tolerance would be heterosis breeding. The degree of dominance ‟a” was in the over-dominance range (a > 1) for most studied cases. The highest estimate of narrow sense heritability (88.15%) was shown by upper stem diameter (SDU) under MD followed by ears/plant (EPP) (83.85%) under LD, while the lowest estimate (0.00%) was shown by anthesis-silking interval (ASI) under LD and MD. The best environment in achieving the highest predicted gain from selection (GA%) was the HD environment for most studied traits followed by the LD environment for grain yield and its components. The highest GA under each environment was achieved by penetrated light at ear (PL-E) under low density (32.13%) and SDU under medium (31.73%) and high density (36.95%).