Variability in Plant Charaters of a Silage Maize Population 'Zea mays, L.' via Two Types of Families

摘要

Variability in the base population had determined through driving two types of families. These were, half-sib (H.S) and first generation of selling (st) families. Hundered entries representing each of those two types of families had evaluated in two different experiments. Family's variance component for S, families was 1.13, 1.28, 2.45, 3.99, 2.81, 1.32 and 1.13 times the corresponding value for half-sib(H.S) families. The estimates of additive variance (cr^) were positive for all studied plant characters. While, the estimates of dominance variance (a2!)) were negative for all characters, the ratio of oV °2g indicated that, additive genetic variance was more effective in controlling plant characters. Genotypic variance among Spfamilies was larger in magnitude than the respective values for half-sib families in each measured plant characters. Meanwhile, environmental variance (a2,,) had reduced in S, families relative to half-sib families in each measured character. Genotypic variation among half-sib families were less than 20% of all studied characters mean values. While, genotypic variations among S[ families were more than 20% of the recorded mean values for most plant characters, except for, days to 50% tasseling and days to 50% silking, thatshowed, variation less than 20% of the characters respective mean values. Heritability estimates were higher in magnitude when calculated from first selfing generation (S]) compared to half-sib families, for all characters, except for, stem girth, that had the same magnitude for the two families. Number of barren plants expressed the least estimates of heritability among all studied characters in each family type (0.83 and 0.86 for half- sib and S| families, respectively). This might indicate the influence of environment in expression of that character. Expected gain from selection in units were the lowest for days to 50% tasseling (0.431 and 0.469 for half-sib and Sj family selection, respectively). Whereas, gain was the highest for ear-leaf area (210.24 and 372.04 for half-sib and S, families selection, respectively). The gain from selection influenced, largely, by the presence of additive variation. The magnitude of genetic advance depends on the magnitude of heritability and some other factors such as selection differential. Accordingly, the expected genetic advance from selection should be higher for S] than half-sib families for the studied plant characters. The expected advance from selecting S] families was about 1.59 times that from half-sibfamilies, as an average for all the studied plant characters.