A note on associations of seed and forage yields with their components in introduced cowpea genotypes under Gezira condtion

Cowpea (Vigna unguiculata (L.) Walp) is an important legume in the tropics and has many uses. In fresh form, the young leaves, immature pods and peas are used as vegetables. The crop is also a great source of livestock feed, and therefore of great value to farmers (Singh et al. 1997). In the Sudan, cowpea is grown in summer under rainfed and in winter under irrigated conditions. However, in the Gezira scheme, cowpea is grown along the irrigation canals, mainly for forage or as a vegetable. Attempts to improve the crop were confined to introduction of improved cultivars from the international agricultural organizations such as the International Institute of Tropical Agriculture (IITA), Nigeria, and evaluation for seed yield adaptation. Cowpea genetic improvements have been given less priority and no breeding programs was undertaken as it is considered as a crop of minor importance. The objective of this study was to identify appropriate selection criteria to improve both seed and forage yields of cowpea. There are many studies on traits associations (correlation and path analyses) Aryeettey and Laing (1973), (Giffens et al. 1994), Nakawuka and Adipala (1999), Vidya and Oommen (2002), Kumari et al. (2003), (Bangar et al. 2004), Gopalan (2006). The experiment was conducted for three seasons (summer, autumn and winter) in 2006 at Gezira University Farm, Wad Medani, Sudan, to quantify association of seed and forage yields with their components. It tested 15 cowpea introduced (Vigna unguiculata (L.) Walp) genotype and laid out in a randomized complete block design (RCBD) with three replications. For summer and winter seasons, the characters measured were seed and forage yields, whereas for the autumn season plant height, days to first flowering, days to 50% flowering, days to pod maturity, number of pods per plant, pod weight, 100-seed weight, seed yield, fresh forage yield and harvest index were measured. There were significant differences among genotypes in all characters only in the autumn season. Seed yield was positively and significantly correlated with number of pods per plant and harvest index, while forage yield was positively correlated with days to first flowering, days to 50% flowering and pod maturity. The path coefficient analysis indicated that number of pods per plant, 100-seed weight and harvest index had the highest positive direct effect on seed yield. Whereas, days to 50% flowering showed the highest positive indirect effect on seed yield through plant height, forage yield and pod weight. Plant height, days to 50% flowering, days to pod maturity, pod weight and seed yield had the highest positive direct effect on forage yield