Analyses of Genotypic Diversity and Adaptability of Cowpea to Humid Tropical Ecology

Abstract

In Africa, cowpea (Vigna unguiculata (L) Walp.) is more appreciated in the food habit than other legumes. It is a popular pulse cultivated mainly in the semi-arid region of West Africa, but its production cannot meet the demand, therefore, this study assessed yield potential and adaptability of cowpea to humid agro-ecology. Ninety-two genotypes obtained from the International Institute of Tropical Agriculture (IITA), Nigeria were evaluated in Calabar (4° 57’N, 8° 19’E) in a randomised complete block design in three replications. All genotypes were collected in southern Nigeria between Latitude 05°05 and 08°30N, and Longitude 03°25 and 15°40E. Twenty-two of the 92 genotypes flowered and had grain yield; TVu-1131, TVu-1132 and TVu-215 had grain yield between 1054.7 and 1093.9 Kg ha-1; this yield is within range of the cowpea yield in West Africa. Principal component analysis (PCA) explained the contribution of 99.9% of the morphological variation in the genotypes and attributed most of it to the diversity in grain yield and single linkage cluster analysis partitioned the genotypes into two groups based on their genetic relationship. There was positive and significant correlation between grain yield and number of days to flowering, number of flowers per plant, number of pods per plant, number of seeds per pod and the pod length; thereby indicating that selection for these pods and seeds characters would lead to improvement of the yield. For the adaptability, cowpea genotypes that are high yielding, photoperiod insensitive and early maturing are most suitable for the environment, in this study TVu-1131, TVu-1132, TVu-215 were identified as adaptable to the humid agro-ecology.