Precision-weighted mixed models identify high-yielding and temporally stable cowpea germplasm across three growing seasons.

INTRODUCTION

Cowpea is an important multipurpose legume that contributes to food and nutritional security, particularly in regions affected by environmental stress. Identifying high-yielding and stable germplasm is essential for improving breeding efficiency and developing resilient cultivars. However, distinguishing persistent genetic merit from seasonal environmental noise remains challenging when trial precision varies among years.

METHODS

Evaluated 150 International Institute of Tropical Agriculture cowpea germplasm lines and four repeated checks over three growing seasons (2020-2022) at a temperate site in Kashmir, India, using augmented block trials. Restricted maximum likelihood and best linear unbiased prediction models accounted for genotype × year interaction and year-specific residual variances.

RESULTS

Seed yield per plant showed high genetic variability (GCV 59.75%), Cullis heritability of 0.991, and prediction accuracy of 0.992. The genotype × year-to-genotype variance ratio was 0.017, while across-year genetic correlations for yield were 0.980-0.998, indicating strong preservation of genotype rankings. Residual variance was markedly larger in 2022, and modeling heterogeneous residuals improved AIC by 50.29. IITA-122 had the highest predicted yield (156.94 g plant-1), 100.60% above the best check, whereas IITA-84 had the best productivity-stability profile (WAASBY 93.85; WAASB 1.61). Thirteen genotypes met an integrated high-confidence selection rule.

DISCUSSION: The selected lines demonstrated persistent genetic merit and temporal stability despite differences in trial precision among years. They warrant replicated, multi-location validation because the present study demonstrates temporal stability at a single location rather than broad adaptation.