Genetic Engineering and Biotechnology, Research Institute, Minufiya University.
Abstract
Gene action, heterosis, potence ratio, inbreeding depression, , genetic coefficient of variation, heritability and predicted genetic advance from selection in the two maize crosses i.e., (M4 xM39) and (M39 x M1 ) were the main objectives of the present study. Six populations in each cross, namely, P1, P2, F1, F2, Bc1 and Bc2 were studied. Most values of mean performance and most variance values in cross-II (M39 x M1) were higher than those of cross-I except number of ears / plant and plant height. Generally, higher heterosis percentage values were detected in the second cross (M39 x M1) for most studied traits including grain yield / plant and some of its components except number of rows / ear, number of ears / plant and tasseling and silking dates. The range of heterosis in cross-I was -6.15% for silking date to 115.96% for grain yield / plant relative to mid parent and –2.55% for silking date to 90.99% for grain yield / plant relative to better parent. Meanwhile, in the cross-II it ranged from -1.85% for tasseling date to 133.60% for grain yield / plant relative to mid parent, while it ranged from 3.61% for silking date to 114.16% for grain yield / plant relative to better parent. Most values of inbreeding depression were higher for the first cross than those of the second one, particularly for grain yield / plant and some of its components. Potence ratio values less than unity were detected in cross-I for ear length and tasseling and silking dates ; and in cross-II for number of rows / ear and tasseling and silking dates indicating partial dominance for these traits. Meanwhile, over dominance values were detected in remaining traits including grain yield / plant in the two crosses, hence, the values were more than unity. In the two crosses, the mean effect of parameters (m) was highly significant and the values were higher in cross-II than their corresponding ones in cross-I except few cases i.e.‚number of kernels / row and number of ears / plant in cross-I. Generally, for grain yield / plant, dominance and epistatic types of gene action additive x additive were obtained in cross-I. Meanwhile, in cross-II dominance gene effects were had the major contributing factor in the performance of this trait. Heritability values for grain yield /plant in the narrow sense reached 86.67%, 92.99% for cross-I and cross-II, respectively, and in cross-I and cross-II for broad sense were 87.49% and 72.37%, respectively. The higher estimates in the broad sense indicating the prevalent of dominance and epistatic effect in the inheritance of grain yield / plant. The expected genetic advance from selection (Dg%) in F2 for grain yield / plant was higher in cross-II (28.39%) than in cross-I (22.55%).
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