Genetic control of the number of heads per plant, spikelets per spike and grains per spike was studied in two durum wheat (Triticum durum Desf.) crosses, Inrat 69/Cocorit71 and Karim/Ben Bechir, respectively. Separate analyses of gene effects were done using means of four generations (parents P1 and P2, F1, F2, and the two reciprocal BC1) at two sites. A three-parameter model was inadequate to explain all traits except number of heads per plant in Inrat 69/Cocorit 71 at one site. In most cases a digenic epistatic model explained variation in generation means. Dominance effects and dominance ´ dominance epistasis (l) were more important than additive effects and other epistatic components. Considering the genotype-by-environment interaction, the interactive model was applied and found adequate in all majority of cases except spiklets per spike and grains per spike in Inrat 69/Cocorit71. The results of this study indicate that maintenance of heterozygosity is useful for exploitation of epistatic effects and adaptability to varied environmental conditions for spiklets per spike and grain per spike in the cross Karim/Ben Bechir. Estimates of narrow-sense heritability indicated that the genetic effect was larger than the environmental effect. The additive effect was the largest component of genetic effects.
Key words: Genetic effects, epitasis, genotype-by-environment interaction,heritability, Triticum durum.
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