GRAIN YIELD AND PHYSIOLOGICAL RESPONSES OF COWPEA GENOTYPES UNDER CONSTRASTING SOIL MOISTURES IN THE SAVANNA AGRO-ECOLOGIES OF GHANA

Abstract

A two-year field experiment was carried out at the Golinga irrigation scheme to evaluate different cowpea genotypes under water deficit and well-watered conditions. The experiment was laid out in a split plot design with three replications of each treatment combination where the main plot was the water supply while the sub plot was the genotype. A non-stress (NS) treatment was based on the supply of irrigation every 3 days compared to a drought stress (DS) which involved the withdrawal of water supply at flowering and podding stage with ten (10) days stressed interval. The plot size for each experiment was 4m × 1.8m (7.2m2), and the spacing between plots and replications were 1m and 2m respectively. Phenological, physiological, morphological and yield data were collected, the data was subjected to ANOVA using GENTAT 12 edition statistical software tool. Means were separated using the least significant difference (LSD) at 5% probability level. It was observed that soil moisture level, genotype and their interaction had significant effect (P<0.05) on the number of days it took for the cowpeas to reach their first flowering. There were significant differences (p<0.05) among the genotype effect of the biomass dry weight and 100 seed weight evaluated. IT17K-1367-2-3, KVx782-1, IT17K-1802-1, IT17K-1707-2 2, IT17K-849-2-1, IT17K-1095-2-2, IT14K-2030-2, UDS-CRS-F20-2, IT17K-1403 1-1 and UDS-CRS-F116-3 were among the outstanding cowpea genotypes with high pod yield, grain yield and harvest index than the rest of cowpea genotypes evaluated and the resistant check IT93K-503-1. The results also revealed that imposition of stress especially at the vegetative stage significantly (p<0.05) reduced the relative chlorophyll contents. The effects of drought were markedly observed in all the parameters studied. High chlorophyll content and high canopy temperature depression was found to be associated with high pod yield, grain yield and one hundred seed weight. The high performing genotypes with high grain yield under drought stress should be evaluated on-farm in order to identify genotypes that are most adaptable to farmers’ growing conditions for release as varieties.