Trait association and stability of virus resistance among cowpea genotypes in Uganda

Abstract

Cowpea (Vigna unguiculata L. Walp) grain constitutes an important source of protein for several households in Sub-Saharan Africa.  However, widespread occurrence of viral diseases is a serious constraint to  productivity of the crop and its nutritional value in terms of grain protein content. This study was carried out to identify cowpea genotypes with the best combination of virus resistance, maturity traits and yield stability.  A screening trial for 105 genotypes was established in three locations (Budaka, Tororo and Serere)  in Uganda for two consecutive seasons to assess for virus resistance, maturity traits and yield. Season and genotypic effects had a greater contribution to the variation in virus infection among genotypes. Eight genotypes (WC48, NE43, NE15, WC35A, WC39, WC33, WC35C, and WC18) showed low virus infection levels.  The three locations formed a single mega-environment with WC51, NE48, and MU17 having the highest mean yield (1,384, 1,191.4 and 1,119.6 kg ha-1), respectively, as well as exhibiting yield stability across locations. Days to first flower, mid-bloom (days to 50% flowering) and days to maturity were positively associated. Virus severity, incidence and AUDPC also had a positive association indicating that indirect selection based on any of these traits is possible. Potential sources of resistance to virus infection exist among the evaluated genotypes. Further screening under high viral  pressure is recommended. The high yielding genotypes are recommended for release for cultivation.

Key Words:   AUDPC, incidence,  severity, Vigna unguiculata