Phenotypic evaluation of gene-pyramided cowpea lines for resistance to Striga gesnerioides using multi-origin inoculum from Nigeria

Cowpea (Vigna unguiculata (L.) Walp.) is a major source of dietary protein in sub-Saharan Africa, but its productivity is severely constrained by the parasitic weed Striga gesnerioides. This study evaluated 140 BC3F2 cowpea lines developed through marker-assisted gene pyramiding for resistance to S. gesnerioides. Two segregating populations were assessed: Population 1 derived from {(IT90K-277-2 × B301) × (IT90K-277-2 × TVu-1272)} and Population 2 from {(IT90K-277-2 × TVu-16514) × (IT90K-277-2 × TVu-1272)}. The BC3F2 lines were screened in a replicated pot experiment using a mixed Striga seed inoculum collected from three major cowpea-producing areas in northern Nigeria. Analysis of variance revealed highly significant genetic variation (p < 0.0001) among lines for both agronomic traits and Striga resistance parameters. Broad-sense heritability estimates ranged from moderate to high, indicating strong genetic control of the evaluated traits. Hierarchical clustering and heatmap analyses identified a subset of BC3F2 lines combining low Striga infestation with favourable yield components, while strong negative correlations were observed between Striga infestation parameters and yield traits. Segregation analysis conformed to a two-gene dominant inheritance model for Striga resistance, with observed ratios fitting the expected 1:1:1:1 distribution (χ2= 2.34). The results demonstrate the effectiveness of marker-assisted pyramiding in combining resistance alleles from multiple donor parents and identify BC3F2 lines suitable for advancement towards the development of cowpea cultivars with stable resistance to S. gesnerioides in Striga-endemic production systems.