Genetic Variance, Heritability and Selection Gain of Maize (Zea mays L.) Adaptive Traits to High Plant Density Combined with Water Stress

The objectives of the present investigation were to determine genetic variance components, heritability and expected genetic advance from selection for agronomic traits of maize under water stress at flowering combined with high plant density; 95,200 plants/ha(WS-HD) as compared with well watering combined with low density; 47,600 plants/ha (WW-LD). Diallel crosses among 6 inbred lines differing in tolerance to both stresses were grown in the field for two seasons using a RCBD design with three replications in two separate experiments; the first under WW-LD and the second under WS-HD. Results across seasons showed that variances due to both additive and dominance were significant, but the magnitude of dominance was much higher than additive variance for all studied traits under WW-LD and WS-HD, except for ears/plant (EPP) and rows/ear (RPE). Narrow-sense heritability (h2n) was the lowest in barren stalks (BS) (3.68 and 4.09%), and the highest in EPP (66.67 and 68.75%) under WW-LD and WS-HD, respectively. The degree of dominance in most cases was over dominance. The estimate of h2n was higher under WW-LD than WS-HD for days to anthesis (DTA), plant height (PH), ear height (EH), RPE, kernels/plant (KPP) and grain yield/plant (GYPP), but were higher under WS-HD than WW-LD for the remaining traits. The non-stressed environment showed higher estimates of genetic advance from selection (GA%) than the stressed one for DTA, PH, EH, BS, KPP and GYPP, but the opposite was true for the remaining traits. The inbreds L20 and L53 carries 75-100% of genes of high yield and its components (except RPE) and genes of short ASI and narrow LANG. Genes of the adaptive traits to stresses (for low PH and low EH) existed in the inbreds L18 and L28. Genes conferring earliness (DTA) existed in L18 and those conferring low BS existed in L28.