Genetic Studies in Some Cowpea (Vigna Unguiculata (L) Walp.) Varieties in Ghana

Abstract

Variation in some growth and y ie ld characteristics were studied in 16 lo ca l and exotic cowpea varieties grown in the country. ELanting was done at three different times of the year representing three seasons. The characters studied were: days to 8C$S germination, days to 5<$> flowering, average dxy weight per plant at 5<?S flowering, number of nodules per plant at 5C$> flowering, percent e ffe c tiv e nodulation, number of branches per plant, number of peduncles per branch, number of pods per peduncle, pod length, number of seeds per pod, 10O-seed weight, days to 5Q& pod maturity, grain y ie ld per plant, grain y ie ld per p lot, resistance towards cowpea mosaic virus (GMV) and shattering in the f ie ld . Separate experiments were also conducted to te s t v a r ia b ility in harvest index,resistance to bruchids in storage and ease o f cooking the dzy seeds without using tenderizers. Analysis of variance indicated that the varie tie s differed significantly from one another in respect of a l l the characters studied. Variety-season interactions also varied significantly fo r most characters studied. Among the yield-influencing factors, only 100-seed weight and harvest index showed significant correlations with grain y ie ld . percent crossability was variable among s ix varieties used as parents in h e r itab ility studies of some quantitative t r a its . There was also selective genotypic cross compatibilities among the varieties used. Narrow sense h e r ita b ilitie s determined fo r 100-seed weight, seeds per pod, pod length, branches per plant, peduncles per branch and pods per peduncle were 80.C^, 74.C$>, 70.C$3, 68.0^2, 3 0 . and 22. respectively. Heterosis in the F s fo r yield-influencing characters was 1 determined at both mid- and better-parent le v e ls . A ll crosses showed heterotic response exceeding \0<2,Z fo r pods per peduncle and grain y ie ld per plant at both le v e ls . Hundred-seed weight and harvest index were found to be of higher sele ctive value than other yield-influencing factors in cowpea improvement. None of the varieties tested f i t t e d the description of an ideal cultivar suitable fo r recommendation to farmers in the country. In order to get a proven variety, i t was suggested that hybridization be used to combine a l l desirable characters into a single compound or multiple cross variety.