Genetics of Harvest and Leaf-Yield Indices in Cowpea

Abstract

Genetics of harvest index and leaf-yield index in cowpea (Vigna unguiculata [L.] Walp) were studied via generation mean analysis to understand the gene action controlling the two traits and to identify the most appropriate breeding strategies for improving these traits. Three cultivars involving IAR-00-1074 with good fodder yield and IT93K-499-35 and IT93K-452-1 with high grain yield were used during 2005 at the Institute for Agricultural Research (IAR), Samaru, Nigeria. The parents, their F₁, F₂ and two backcross generations were evaluated using a randomized complete-block design. Highly significant differences were observed among the five generations for harvest index and leaf-yield index. F₁ means were closer to the parent with higher harvest index for both crosses. This suggested that dominance was involved in expression of harvest index. The same trend was observed for leaf-yield index. Backcrossing to both parents showed good convergence of genes on the recurrent parent in the cross IAR-00-1074 × IT93K-499-35. Non-additive gene action significantly contributed to total genetic variations in both traits for the two crosses. Narrow-sense heritability estimate for harvest index was low for the two crosses IAR-00-1074 × IT93K-452-1 (20%) and IAR-00-1074 × IT93K-499-35 (17%), and moderate for leaf-yield index in the cross IAR-00-1074 × IT93K-499-35 (32%). Expected genetic gain in the F₃ over the F₂ means was low for both traits in the two crosses. For genetic improvement of harvest and leaf yield indices, inter-mating selected segregates in early generations should be an effective approach.

KEYWORDS:

• Vigna unguiculata
• genetic gain
• heritability
• variance components