Abstract

Thirty-six F₁ hybrid crosses and nine parental lines were evaluated in two environments to estimate General Combining Ability (GCA) and Specific Combining Ability (SCA) effects on seed yield traits. Diallel results based on Griffing B method 2 revealed highly significant differences for all traits tested for GCA and SCA except plant height which revealed the existence of both additive and nonadditive gene actions for the inheritance of the relevant traits. The magnitude of GCA variance was considerably higher than that of SCA variance except for top diameter, and fresh stem weight with leaves and pods, showing the additive gene action predominates for these traits. In both conditions, Hayman and Jinks’s graphical studies demonstrated that partial dominance controlled various seed yield traits such as plant height and days to first flowering. On the other hand, pods yield and the majority of physical traits indicated either dominance or overdominance gene action. Plant height, fresh stem weight with leaves and pods, and pods per plant, all had a strong positive relationship with seed yield. These variables also had a higher proportion of additive effects, a higher baker ratio and a moderate narrow-sense heritability, indicating successful indirect selection for seed yield. The parental lines P₆, P₇ and P₉ were identified as good general combiners for seed yield contributing traits. The hybrids P₁ × P₄, P₂ × P₈, P₃ × P₈, P₄ × P₆, P₅ × P₇, P₆ × P₉ and P₇ × P₉ outperformed the parents in terms of heterotic responses and showing that they have a lot of genetic potential for kenaf enhancement in tropical climates.

Keywords: Gene action; Combining ability; Potence ratio; Seed yield; Kenaf