Genetic analysis of seed proteins contents in cowpea (Vigna unguiculataL. Walp.)
In order to select cowpea genotypes with high food value, 10 varieties were genetically screened in Ngaoundéré (Cameroon) for seed crude protein and its soluble fractions contents. Five divergent lines were studied through a 5 x 5 half diallel cross mating. The genotypes presented a significant genetic variability for these parameters (p < 0.05). The globulins constituted the major seed protein fraction, followed by albumins. Diallel analysis demonstrated that, both additive and non-additive gene effects were responsible for the genetic variation of these traits. However, dominance variance was more important than additive variance for all traits. The model of over-dominance was most widespread, suggesting delayed selection to fairly good improvement. All these parameters were found highly inheritable (h2 = 0.68 to 0.83). The parents differed significantly for their general combining ability (GCA) and the F1 progenies showed specific combining ability (SCA). Dominant genes have positive effects for high levels of albumins, globulins and prolamins, while high percentage of seed protein and high glutenins content appeared to be associated with recessive genes. In the Guinea savannah zone, these results would help breeders to improve these biochemical traits in terms of initial parent selection and subsequent crossbred selection and breeding procedures.
Key words: Vigna unguiculata, seed crude protein content, soluble protein fractions, diallel analysis, genetic improvement, Guinea savannah zone.