Yield and stability of new cowpea varieties in Zimbabwe

Abstract

Cowpea (Vigna unguiculata [L.] Walp) is highly nutritious and fits well in smallholder crop-livestock farming systems of sub-Saharan Africa. Newly developed cowpea varieties need to be assessed for grain yield performance and stability across environments. Furthermore, a comprehensive understanding of the test environments is crucial in rationalising resources for breeding programmes. The objective of this study was to identify high yielding and stable cowpea genotypes, and determine the ideal (representative and discriminating) testing environments for cowpea in Zimbabwe. Fifteen cowpea genotypes were evaluated at 5 locations, for 2 years under rain-fed conditions. Combined analysis of variance for grain yield across locations and years showed highly significant (P < 0.001) genotype x environment interaction (GE). The variance component due to GE was 6 times larger than that of genotypes. Genotype plus GE biplot showed that environments studied were actually in one mega-environment; and Harare Research Station (HRS) was identified as desirable discriminating and representative environment. Genotypes G1, G11 and G3 were high yielding and more stable than the check varieties, G4 (CBC2) and G7 (CBC3). These genotypes are suitable for release; while HRS is recommended for culling inferior genotypes during early generation testing.

Key Words:  Biplot, sub-Saharan Africa, Vigna unguiculata