5201
ABD EL-SAMAD MAHMOUD YOUNIS
INHERITANCE OF SOME ADAPTIVE TRAITS TO HIGH PLANT DENSITY AND DROUGHT TOLERANCE IN MAIZE
Maize, High Plant density, Water deficit, Gene action, Combining ability, Adaptive traits, Response, Tolerance, Heritability, Heterosis
Enhancement of maize productivity from land unit area in Egypt could be achieved via growing tolerant hybrids to high plant density (HD) stress in combination with using the optimum plant density irrigation. A set of inbred lines with obvious diversity in their adaptive traits to HD and water stress (WS) were used in the present study as parents of diallel crosses (without reciprocals) to study the inheritance of these traits, identify tolerant genotypes to HD and water stress and determine the optimum plant density and irrigation for maximizing grain yield/fed (GYPF). The F1 crosses were made in 2012 and evaluation of inbreds and hybrids were carried out in 2013 and 2014 seasons, at the Agricultural Experiment and Research Station, Faculty of Agriculture, Cairo University, Giza, Egypt. A split-split plot design in randomized complete blocks arrangement with 3 replications was used, where main plants were devoted to irrigation treatment (well watering (WW) and water stress (WS)), sub-plots to plant densities (20, 30 and 40 thousand plants/fed) and sub-sub plots to maize genotypes. Some newly developed maize hybrids that characterized by more ears/plant (EPP), narrow leaf angle (LANG), short anthesis-silking interval (ASI), less barren stalks (BS) and less plant height (PH) and ear height (EH) gave very high grain yield(GYPF), reaching 51.16 ard/fed in the cross L20 × L53 when grown under high plant density (40,000 plants/fed) and were given well watering. Moreover, some crosses L53 × Sk5, L53 × Sd7, L20× L18 Sk5 × L28) gave > 46 ard/fed under 40,000 plant density. GYPF of all studied genotypes showed a quadratic response of increase to the six environments from low to high levels, except L18, L28, Sd7 inbreds, which showed a quadratic response of decrease. The inbreds L53, L20, Sk5 proved to be tolerant (T), while L18, L28, Sd7 were sensitive (S) to HD and/or WS. T×T group of crosses exhibited better values in most studied traits than T×S and S×S groups of crosses under both stresses. Both dominance and additive variances were highly significant, but the estimates of dominance were much higher, in magnitude, than additive variance for all studied traits under all environments, suggesting that heterosis breeding is the method of choice for improving adaptability traits to both HD and WS stresses. The degree of dominance was over dominance in all cases. For all studied traits under all environments, broad-sense heritability was of high magnitude (ca. 90%) and narrow-sense heritability was generally of small magnitude, but reached about 67% in EPP and RPE. Expected genetic advance from selection (based on 10% selection intensity) was generally of small magnitude, but reached its maximum for grain oil content (GOC) under most studied environments. The traits KPP, EPP, ASI and BS proved to be the best selection criteria for improving productivity under severe stress of both HD and WS together.
2016
Ph.d
Cairo
Agriculture