Lead Selection Traits Relationship in Cowpea (Vigna unguiculata (L.) Walp.): Is Grain Yield Still Key?

A field study was set to highlight the relationships and contributions of yield and yield-related traits to the choice of a superior cowpea variety. Five cowpea varieties, Sampea-7 (IAR 48), Sampea-8 (IAR 452-1), Sampea-10 (IAR 499-35), Sampea-11 (IAR 288) and Sampea-12 (IAR 391) were evaluated under normal growing conditions during the 2011/2012 growing season at the University of Calabar Teaching and Research Farm. The analysis of variance (ANOVA) for a randomized complete block design (RCBD) with three replications did show significant (P = .05) varietal differences for days to 50% flowering (50% FLW), days to 75% maturity (75% MTY), number of pods per plant (NPP), seed size (SDS), total plant biomass (TOB) and grain yield (GRY). The number of branches (NBR), pod length (PDL) and harvest index (HI) were not significantly different. The GRY had a positive correlation with all other yield-related traits except for the flowering traits and breeding for the former traits will be an indirect way to select for high grain yields. However, based on the weighted combined contributions of all the traits, the superiority of the varieties, Sampea-7 and Sampea-8, which were significantly different, followed an order different from their average grain yield order. Apparently, this re-ordered result highlights that the choice of a high performing cowpea variety could not be viewed as a function of high grain yield but a collective contribution of all other yield-related traits. These findings suggest that placing huge emphasis only on the economic yield (in this case, grain yield) as the main selection index could possibly fault the breeding and evaluation of superior cowpea varieties