Analysis of Parent Offspring Regression of Selected Cowpea (Vigna unguiculata [L]. Walp.) Agronomic Traits in Phosphorus Limiting Soil

Cowpea is a significant grain legume pulse, vegetable, and fodder crop. However, due to biotic and abiotic stresses, yields have been consistently low. Phosphorus (P) deficiency-related yield losses are one of the major abiotic stresses. The objectives therefore were i) to evaluate the mean performance response of selected cowpea traits across genotypes in optimum and P- limiting soil media and ii) to determine the cowpea heritability response of agronomic traits in P-limiting soil. Twenty cowpea genotypes comprising of 12 F1 crosses and eight progenitors were evaluated at the University of Zambia Greenhouse in Lusaka, using a completely randomized design with three replications and two-level sets of phosphorus (i.e. 0 kg P2O5 and 60 kg P2O5). The 60 kg P2O5 level set was used as a control. The results showed that the mean performance across genotypes for all measured traits was higher in control experiment at an applied rate of 60kg P2O5/ha than at applied rate of 0Kg P2O5/ha experimental sets. Significant better performances were obtained with plant height, shoot biomass, plant biomass and yield measured traits. The narrow sense heritability for measured traits ranged from 11- 35 % and 12 - 72% for 0 Kg P2O5 and 60 Kg P2O5 experimental set respectively. The highest narrow sense heritability scores in experimental set were pod length (h2= 0.35) and root biomass (h2= 0.28) while in the control set the variable yield (h2= 0.72) had the highest score. This implies that the identified trait (pod length) with high narrow sense heritability in P-limiting soil can initially be used to aid in selecting for high performing genotypes in P limiting soil. However, this should be supplemented by yield response especially in late generation selection (F5 onwards).