Physical and biochemical basis of resistance in cowpea [Vigna unguiculata (L.) walp.] accessions to pulse-beetle, Callosobruchus chinensis (L.)

Laboratory studies were conducted in 52 accessions of cowpea including check (Local variety) for variability in physical parameters of seed viz., colour, shape, texture, length, width, hardness, seed coat hardness and 100 seed weight and biochemical parameters namely, moisture, phenols, tannins and α-amylase inhibitor activity to understand the basis of resistance against pulse beetle. Significant differences among the cowpea accessions were observed for all the physical and biochemical parameters. Based on growth index of pulse beetle, Callosobruchus chinensis, eleven accessions viz., IC107466, 106815, 106037, 106812, 106816, 106817, 108749, 311138, 328859, 381583 and Pusa komal were found to be resistant to the beetle. Correlation coefficients between growth index (GI) of pulse beetle and physical and biochemical parameters of cowpea indicated that GI of C. chinensis had insignificant relation with seed hardness and seed coat hardness. The GI of beetle had a positive relation with seed length-width ratio, 100 seed weight and seed moisture. Phenol and tannin had negative relation with GI of C. chinensis while amylase inhibitor had a positive relation.