Evaluation of Cowpea [Vigna unguiculata (L) Walp.] Germplasm against Pulse Beetle, Callosobruchus chinensis (L.) and Correlation with Morphological Seed Characters

Abstract

Background: In India, cowpea (Vigna unguiculata (L) Walp) is a minor pulse and is cultivated mainly in arid and semi arid tracts. Cowpea grains are often completely destroyed by bruchids both quantitatively and qualitatively making them unfit for planting, marketing and human consumption. Therefore, development and use of tolerant/resistant cowpea cultivars offer a simple, cheap and attractive way for reducing bruchids damage. Hence, the present study was aimed to identify new sources of insect resistant traits against Callosobruchus chinensis in cowpea germplasm so as to incorporate them in cowpea crop improvement programmes to evolve resistant or tolerant varieties against bruchids. Methods: Twenty seven cowpea genotypes were evaluated for resistance or susceptibility to pulse beetle, C. chinensis (Coleoptera: Bruchidae) using no-choice artificial conditions. Various parameters viz., oviposition, adult emergence/20 seeds, percent adult emergence, mean developmental period, per cent seed weight loss and growth index were determined for each genotype. Result: Significant differences were observed among cowpea accessions in terms of growth index (GI) of bruchid. Based on GI, one accession (IC 257844) was found moderately resistant (MR). Although, cowpea accessions showed variation in physical seed characters viz., seed coat colour, shape, seed length, seed width, seed thickness and 100 seed weight, they could not exert significant influence on any of the insect biological characters. Based on the study, it was demonstrated that IC 257844 (categorized as moderately resistant) could be used as potential donor for the development of bruchid tolerant cultivars.