Detection of epistasis for plant height and leaf area per plant in maize (Zea mays L.) from generation means analysis.

The role of gene action and interactions in the inheritance of two physiologic traits in maize was ex- amined through generations' means analysis in a field study during 2005 and 2006 at CCRI, Pirsabak, Nowshera, Pakistan. A total of 20 genotypes including 4 parents, 4 F1s, 4 F2s, 4 BC1s and 4 BC2s were evaluated in a random- ized complete block design with 3 replications. Data were recorded for leaf area and plant height on plant basis. A combined analysis of variance for generation means across years was carried. Genetic effects were estimated by method of weighted least square, using appropriate weights (coefficients) for each generation mean equation. Significant differences among generation means were indi- cated. Chi square values were significant for all crosses in both traits according to a joint scaling test. Six parameters model was applied to accommodate the digenic epistatic interactions. Significant dominance effects were indicated in all crosses for both traits and these effects were much higher in magnitude than their corresponding additive ef- fects. All crosses in the study also indicated significant ad- ditive x dominance effects for leaf area. Significant addi- tive x additive effects were also present in some crosses for the two traits. Complementary and duplicate gene in- teractions appeared operative in the inheritance of leaf area trait. Duplicate gene interactions were seen function- ing in controlling plant height in most crosses. Epistasis played a considerable role in controlling leaf area and plant height traits. Improvement in these two physiological plant traits could be much slower in a selection program.