Evaluation of cowpea root system and yield traits in humid tropical agro-ecology

Roots are essential to plants and can be the focus for yield improvement in the environment the plant grows. The objectives of this study were to evaluate some yield components and root traits in cowpea (Vigna unguiculata (L) Walp) and establish the linear association between the yield and root traits to explore improvement potentials of the crop in humid ecosystem. Ten cowpea accessions were tested in Calabar, Nigeria with humid tropical rainforest ecology. The accessions were grown in perforated polyethylene pipes arranged in completely randomized design, in five replications and on the field arranged in a randomized complete block design, in three replications. TVu-215 had longest roots, heaviest root biomass and largest root volume. TVu-10983, TVu-1515 and TVu-7906 also had long roots. TVu-7857, TVu-1130, TVu-1131, TVu-215 and TVu-1515 had the greatest root density. With respect to yield traits, TVu-1131 and TVu-16196 had the highest yield per hectare; TVu-7857 also had high yield per hectare. Root traits did not significantly correlate with most of the yield traits, but there was significant negative moderate correlation (-0.51) between root volume and number of pods per plant. Root of cowpea does not require much robustness in humid ecology to absorb water and nutrient, which accounts for the non-significant correlation between root system and yield traits in the environment. TVu-16196, TVu-1130, TVu-1131, TVu-215, TVu-7857 and TVu-1515 are selected for the improvement of the root and yield traits. Key words: Cowpea yield traits, root traits, humid tropical ecology, Calabar, Nigeria.