Physical and biochemical attributes of seeds for screening cowpea genotypes for resistance to cowpea weevil {Callosobruchus maculatus (f.)}

Abstract

Cowpea weevil {Callosobruchus maculatus (F.)} is an important field-to-store pest responsible for post-harvest loss of
cowpea {Vigna unguiculata (L.) Walp.} seeds. One of the most economical and environment-friendly ways of preventing
losses from the beetle is through the use of resistant cowpea genotypes. Physical and biochemical attributes of seeds play
a key role in conferring resistance to the pest. Therefore, seeds of twenty-three cowpea genotypes were assessed for
resistance to weevil infestation, nutritional and anti-nutritional factors. Relationship between the resistance parameters and
the biochemical components of the seeds were also examined with the use of correlation analyses. Results showed that
variability existed among the cowpea genotypes for seed physical resistance parameters such as initial seed weight,
residual seed weight, seed weight loss, number of damaged seeds and weight of undamaged seeds. Association of
reproductive efficiency with carbohydrate content, crude fibre and moisture content in the cowpea was positive and
significant (r = 0.43*, 0.45* and 0.73**) while its relationship with protein content was negative and significant (r=-
0.46*). The ash content correlated negatively and significantly (r=-0.46*) with the median developmental period. Cowpea
genotype IT08K-125-107 exhibited the highest degree of tolerance to C. maculatus infestation, having suffered neither
weight loss nor damaged seed and also had very low reproductive efficiency of the C. maculatus. The study concluded
that while biochemical components played very little role in conferring resistance to C. maculatus in cowpea, increased
carbohydrate content, crude fibre as well as reduced ash and protein content in the cowpea seeds decreased the
reproductive efficiency and intensity of the C. maculatus infestation