Genetic variability for tolerance of drying injury in seed corn (Zea mays L.)

Bdliya, Paul
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Research was conducted to study the influence of parentage and to assess the degree of contribution of the various genetic components in the variation for tolerance of seed to high drying temperature among six maize inbred lines;The inbred lines (A632, A641, B14A, B73, Mol7 and W64A) selected for this study were based on the seeds' previous history of susceptibility to drying injury. Diallel crosses among the six lines were made by hand in 1984 and 1985. Seeds were harvested at two different times; a high moisture harvest (ca. 50%) and a low moisture harvest (ca. 35%). Seeds from each harvest were dried to 12% at either 50 C or 35 C. Hybrid seeds were evaluated in the laboratory for tolerance of drying injury using five seed quality traits--warm (standard) and cold germinations, 100 kernel weight, seedling dry weight and shoot/root ratio;Analyses of inbred means, combined for both years, indicate that larger and significant (P < 0.05) variability exists among lines when used as seed rather than as pollen parents for warm and cold germinations when seeds were dried at 50 C. The influence of inbreds as pollen parents was not significant, as assessed by cold germination, in any of the treatment combinations. For 100 kernel weight, seedling dry weight and shoot/root ratio, variability observed among inbred means used as seed or pollen parents were however significant (P < 0.05). This, perhaps, was due to heterosis;General combining ability (GCA) and maternal gene effect mean squares were significant (P < 0.01) and larger than those of specific combining ability (SCA) and reciprocal components for the five seed quality traits in the four treatment combinations. This indicates that both additive and maternal gene effects were more important than nonadditive, dominant and reciprocal gene effects in the variation for tolerance of drying injury among these six lines. Environment (year), however, had a significant (P < 0.01) effect on the contributions of these genetic components.