Genetic Analysis of Water Stress Tolerance Attributes in F1 Maize Diallel Crosses

Abstract

A half diallel set of crosses involving 10 inbred lines of maize along with commercial hybrid ARCGH 128 were evaluated at two different irrigation treatment during two season 2019 and 2020 using RCBD design with three replications at two locations (Minia and Assuit governorates), to determine combining ability and gene action for grain yield and its components. the most superior crosses for the economic traits were detected in L1 X L2 for leaf proline content, ear weight and number of rows/ear, L1 X L8 for number of ear /plot and number of rows/ear, L4 X L9 for Days to tasseling and Days to silking, L3 X L8 for Leaf angle, leaf rolling, number of kernels/ear, number of rows/ear and number of kernels/row and L3 X L10 for days to tasseling, days to silking,leaf rolling, relative water content (RWC %), kernel fresh weight, number of rows/ear and yield. Highly significant and larger in magnitude values of dominance (H1 and H2) components were found to be at the significant level at (5%) for all studied characters which confirmed their importance in the expression of these characters. However (D) dominance component was reached to the significant level only for the normal irrigation treatment for the leaf angel at both locations, all irrigation treatment for leaf proline content at both locations, normal irrigation treatment for number of kernel/row at Assuit location and all irrigation treatment for 100 kernel weight and number of ear/plot at both locations. The (F) component was significant and positive for all irrigation treatment for leaf proline content at both location, normal irrigation treatment for number of kernel/row at Assuit location, all irrigation treatments for 100 kernel weight at both location, stress irrigation treatment for number of ear/plot at Minia location. Significant differences of environmental variance (E) components were recorded for all irrigation treatment for leaf rolling at Assuit location, all irrigation treatment for ear weight at Minia location and all irrigation treatment for number of rows/ear and number of ear/plot at both locations. Dominance component of variance (H1 and H2) were significant and/or highly significant for all studied traits and (H1) was greater than (H2) in F1 indicating that positive and negative alleles at loci of these trait were not in proportional equal for parents. The estimator (h2) were refers to the dominance effect overall heterozygous loci was significant for all studied traits except days to tasseling for normal irrigation treatment at both locations, stress irrigation treatment for leaf angel at Minia location, all irrigation treatment for leaf rolling at both locations, normal irrigation treatment for ear weight/kg/plot at both locations and for stress irrigation treatment for number of rows/ear at Minia location. Average degree of dominance (H1/D) 0.5 was more than unity for all traits, these finding indicated the involved of an over dominance expression for all characters. However the over dominance observed in such character may not be an index of true over dominance could be based due to linkage epistasis or both together. Since the ratio of dominance (KD) recessive (KR) alleles was more than one for all the studied characters, these indicates a preponderance of dominant gene in the parents for the characters. The value of K (h2/H2, which stands for the number of groups of genes that exhibit dominance for each character) was <1 for all the studied characters for normal irrigation treatment at Assuit location and all irrigation treatment at Minia location and all irrigation treatment at Minia location for number of rows/ear and 100 kernel weight/gm. This suggested that just one group of genes showed dominance governed all of them while this parameter could be underestimated, when the dominance effects of all genes was not concerned with equivalent, size and distribution, where the distribution of genes was correlated, or complementary gene interactions occur. Heritability values in bored sense (h2b) were relatively low for all characters. However, heritability in narrow sense (h2n) was high scored values more 50% except leaf rolling for stress irrigation treatment at Minia location (0.48%) these results confirmed that the environmental effects constitute a major portion of the total phenotypic variation in these characters.