A study of the Genetic Behaviour of Some Yield Traits in Half Diallel Crosses of Maize (Zea mays L.)

A half diallel set of crosses among six inbred lines of maize were evaluated at the Maize Research Department (G.C.S.A.R.) in Damascus Governorate during 2010 and 2011 growing seasons to estimate heterosis and combining ability components for the number of rows per ear, number of kernels per ear, ear length (cm), ear diameter(cm), 100-kernel weight (g), and grain yield (ton /hec). The inbred lines, crosses, general combining ability (GCA) and specific combining ability (SCA) mean squares were highly significant for all the studied traits, showing the existence of a genetic variance among lines. The ratios of GCA to SCA detected for the studied traits showed the dominance of an additive gene action for all the studied traits except for 100-kernel weight and grain yield which showed the predominance of a non-additive gene action. The heterosis percentage for the studied traits was significant based on mid and better parents. The GCA effects showed that the lines CML.317, CML.371, CML.373 and CML.367 were good general combiners for grain yield, while the SCA effects showed that seven hybrids were the best F1 cross combinations such as (CML.317×CML.371) for grain yield.

Heterosis and inbreeding depression in populations of maize (Zea mays L.)

This research was conducted at the Department of Maize in the General Commission of Science Agriculture Research (GCSAR) Damascus, Syria. The genetic material included parental inbred lines and the first and second (F1, F2) generations of two hybrids of maize to estimate the heterosis, degree of dominance and the inbreeding depression under two treatments of irrigation. Results showed that mean squares of inbred lines P1, P2 and the first generation were non significant for all studied traits, while the variance of the second generation F2 was highly significant under the stress and non stress treatments, The hybrid (IL.275–6×IL.362–6) showed the highest average of yield under stress and non stress treatment, a Positive heterosis effect relative to mid parents and the better parent was recorded for ear height, ear diameter, 100 kernels weight and yield per plant, The degree of dominance showed that the branches per tassel was controlled by partial dominance on the other hand the ear diameter and yield per plant showed the greatest values of inbreeding depression, Results revealed the effective selection among the F2 individuals of the studied hybrids specially the hybrid (IL.275–6× IL.362–6) through the late generations (S5, S6) to get new inbred lines of maize which had dominance desirable alleles to improve yield and it's components especially under water stress conditions.