Phenotypic Evaluation of Gene-Pyramided Cowpea Lines for Striga Resistance Across Nigerian Ecologies

Cowpea ( Vigna unguiculata [L.] Walp.) is a critical protein source in sub-Saharan Africa, but its production is severely constrained by the parasitic weed Striga gesnerioides. This study evaluated two BC₃F₂ populations (140 lines). Population 1 was developed from {(IT90K-277-2 × B301) × (IT90K-277-2 × TVu-1272)} and Population 2 from {(IT90K-277-2 × TVu-16514) × (IT90K-277-2 × TVu-1272)}. Lines were screened against a homogeneous mix of Striga seeds from three endemic Nigerian environments (Kano, Borno, Jigawa) in a replicated pot trial in the screen house. Phenotypic evaluation revealed significant genetic variation (p < 0.0001) for both cowpea agronomic and Striga resistance parameters. Broad-sense heritability was high for Striga resistance parameters and yield components indicating their genetic control. Hierarchical clustering identified resistant BC₃F₂ lines in Cluster 1 that combined Striga resistance with high pod and seed weights, demonstrating no yield penalty. Conversely, Cluster 3 exhibited high susceptibility and poor yield. Strong negative correlations (r < − 0.8) confirmed the negative impact of Striga on yield. Genetic architecture analysis supported a two-gene dominance model for Striga resistance BC₃F₂ populations, validated by chi-square tests (χ² = 2.34; expected 1:1:1:1 ratio). These Striga resistance pyramided lines exhibit broad-spectrum resistance to S. gesnerioides from Kano, Borno and Jigawa, providing a validated breeding population for deploying durable, high-yielding cowpea varieties in Striga-endemic and major cowpea growing regions of Nigeria