Analytical Assessment of Yield Stability of Cowpea Varieties Across Environments in the Sudan Savanna Zone

Yield stability analysis identifies varieties that perform consistently across diverse environmental conditions, and its application to cowpea breeding materials for the Sudan savanna zone provides breeders and extension advisors with evidence-based variety recommendations that account for genotype-environment interaction. This study analytically assessed the yield stability of twelve cowpea varieties (eight advanced IITA lines and four commercial varieties) across nine environments in Sokoto, Katsina, and Jigawa States over three seasons (2021 to 2023). A multi-environment trial methodology was employed using AMMI (Additive Main effects and Multiplicative Interaction) analysis and GGE biplot to characterise genotype-environment interaction and identify stable high-yielding varieties. Grain yield data were collected from nine sites per season. AMMI analysis showed that environment explained 54.7 percent of total grain yield variance, genotype 18.3 percent, and genotype-environment interaction 27 percent. GGE biplot analysis identified IT97K-499-35 as the most stable high-yielding variety across the nine test environments, with a mean yield of 1.47 t ha-1 and low AMMI stability value. ICTV 0-5 showed the highest mean yield (1.63 t ha-1) but was highly environment-specific, performing best only in Sokoto environments. The study fills a yield stability analysis gap for Sudan savanna cowpea systems and recommends IT97K-499-35 for general recommendation across the zone while designating ICTV 0-5 for recommendation in the highest-yielding Sokoto environments only.

Keywords: yield stability, cowpea, Sudan savanna, AMMI analysis, multi-environment trial