Assessment of morpho-variability between bruchid tolerant AND SUSCEPTIBLE cowpea (Vigna unguiculata L. Walp.) accessions

Abstract

Cowpea bruchid is a major constraint to cowpea production. Easy identification of resistant/tolerant accessions to bruchid infestation has been a major challenge in bruchid resistant breeding programmes. Hence, the study was aimed to evaluate variations in some morphological characters between some bruchid resistant/tolerant and susceptible cowpea accessions, correlating them with their bruchid tolerance status in the hope of identifying a pointer character(s) that can facilitate easy identification of bruchid tolerant among cowpea germplasm. Sixty accessions were collected and evaluated for bruchid tolerance. Accessions were then grouped into bruchid susceptible and bruchid tolerant. These accessions were planted in Randomized Complete Block Design with ten replicates. Morphological differences between groups were evaluated accordingly. Of the sixty accessions evaluated, fifty-two were susceptible while eight were bruchid tolerant. No qualitative differences were observed between bruchid susceptible and tolerant groups, however significant differences were observed in quantitative characters which include terminal leaflet length, terminal leaflet/width ratio, leaf petiole length, terminal leaflet petiole length (TLPL), leaf petiole length, pod length (PDL), pod width, total number of pods per plant, seed length (SDL), seed width (SDW), seed thickness (SDTK) and 100 seed weight (100SDW). Bruchid tolerance was significantly positively correlated with seed characters which include, SDL (r = 0.798, p < 0.01); SDW (r = 0.798, p < 0.01); SDTK (r = 0.758, p < 0.01);
100SDW (0.830, p < 0.01) and significantly negatively correlated with TLPL and PDL (p < 0.05). These characters can provide easy identification of bruchid tolerant among cowpea germplasm, hence requires further investigations.

Keywords: Cowpea, Vigna unguiculata, Bruchid, Callosobruchus maculatus, Morphology