Genetic Parameters Controlling Inheritance of Agronomic and Yield Traits of Maize (Zea mays L.) under Elevated Plant Density

The objectives of the present investigation were to determine the type of gene action, heritability and expected genetic advance from selection for agronomic and yield traits of maize under high plant density (HD) stress and low density (non-stress) and to identify the parents that carry favorable genes for adaptive traits to HD tolerance. Plants of diallel crosses among 6 parents differing in HD tolerance were grown in the field along with their parents for two seasons using a randomized complete block design with three replications in two separate experiments; the first under HD (95.200 plants/ha) and the second under low density (LD) (47,600 plants/ha). 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 12 studied traits under HD and LD, except for ears/plant (EPP) and rows/ear (RPE), suggesting that heterosis breeding would be more efficient than selection for improving such traits. Narrow-sense heritability (h2n) was of small or medium magnitude, but reached to 67.02% for RPE under HD. The degree of dominance in most cases was over dominance. In general, seven traits (anthesis silking interval; ASI, plant height; PH, ear height; EH, barren stalks; BS, RPE, kernels/ear; KPR and 100 kernel weight; 100 KW) showed higher h2n and expected selection gain (GA%) under HD than LD environment, while the remaining five traits (days to anthesis; DTA, leaf angle; LANG, EPP, KPP and grain yield/plant; GYPP) showed opposite trend. The inbreds L20, L53 and Sk5 carry genes of high yield and most of its contributing attributes. Genes of low BS are found in L20 and genes of narrow LANG in L53, Sk5 and Sd7. Genes of low PH and EH are found in L18 and L28. Genes of high RPE and short ASI are found in Sd7. Genes for earliness (DTA) exist in L18 and Sd7.