Thesis (M.Sc.) - Cairo University - Faculty of Agriculture - Department of Agronomy

Maximizing maize productivity from land unit area in Egypt could be achieved via growing hybrids that withstand plant density stress. A set of 23 inbred lines chosen on their plant density (PDT) and drought tolerance were used tested in the present study using line x tester analysis. The objectives were to identify the best inbreds in general combining ability (GCA) effects, the best testcrosses in specific combining ability (SCA) effects and the best genotypes in PDT and to study the inheritance of adaptive traits to PDT. The testcrosses with three testers were made in 2015 and evaluation of inbreds, testers, hybrids and check cultivars was carried out in 2016 season, at the Agricultural Experiment and Research Station, Faculty of Agriculture, Cairo University, Giza, Egypt. A split plot design with 3 replications was used, where main plots were devoted to 3 plant densities, namely low (LD), medium (MD) and high (HD) (20, 30 and 40 thousand plants/fed, respectively) and sub plots to 100 maize genotypes. Some newly developed maize hybrids gave very high grain yield/fed, reaching 50.69 ard/fed in the testcross L28 {u00D7} Sd7 under a density of 40,000 plants/fed. The best inbreds in GCA effects were L28, IL51, L21, L17, L14, IL84, IL15 and IL53 and the best testcrosses in SCA effects were IL84 {u00D7} SC10, L21 {u00D7} Sd7, IL151 {u00D7} Giza2 and IL51 {u00D7} Giza2, under high plant density. The inbreds L21, IL15, IL53, Inb176, IL80, L28, IL151 and L14 in adescending order proved to be tolerant (T) and some inbreds were sensitive (S). 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, indicating that heterosis breeding is the most appropriate procedure for improving PDT in maize

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