engleski

GENETIC EFFECTS FOR GRAIN YIELD IN MAIZE HYBRIDS

Grain yield as agronomically the most important trait in maize is a quantitative trait determined by many genes whose effect is modified by environmental conditions. Knowledge about the nature of gene action involved in conditioning the expression of grain yield is essential to optimizing breeding progams. The objective of this study was to evaluate the genetic effects including digenic non-allelic interactions for grain yield by using generation mean analysis for three single crosses of maize. Six generations were analyzed per each observed hybrid: P1, P2, F1, F2, and the first backcrosses to respecting parents (BC1.1 and BC1.2). Experiments were conducted at two locations in 1996 and 1997. The six generations were evaluated on individual plant basis with sample size of minimum 50 plants for parents to 250 plants for backcross and F2 generations at each location. The additive/dominance model was adequate according to Goodness-of-fit test using c2 statistic. All three crosses had considerably greater estimates of dominance parameters across all locations, inidicating mainly dominant gene effects (d). The magnitude of non-allelic interactions, however, were environment-dependent. Additive ´ additive effects (aa) were consistently positive and dominance ´ dominance effects (dd) correspondingly negative. The two categories of effects were approximately one third to one fifth of d, depending on location. Dominance ´ dominance epistasis (dd) prevailed over other types (aa, ad) in most instances. According to consistently opposite signs of d and dd, it seems that the dd interactions were mainly of duplicate, dominant epistatic or recessive suppressor kind. These results suggest that dominance and duplicate epistatic effects were of primary importance for grain yield in maize hybrid investigated. However, estimates of gene effects might be biased with the response to different environmental patterns.

maize; grain yield; genetic effects

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