Influence of plant and seed characteristics on cowpea weevil infestation of Vigna unguiculata

Cowpea (Vigna unguiculata) is a self-pollinated popular legume that can be consumed as vegetable, grains stew or otherwise used for animal forage. It is only propagated by seed. Cowpea weevil (Callosobruchus maculatus) is a field and storage pest which results in poor quality seed upon infestation. It can cause up to 100 % loss when cowpea seed is stored without any form of seed treatment hence the study was carried out to determine how plant and seed characteristics influence weevil infestation of seed. The field and lab experiments were carried out in Jomo Kenyatta University of Agriculture and Technology (JKUAT) between October 2016 and August 2017. Plant and seed characteristics were measured. Seed biochemical composition (protein and tannin content) were evaluated following the AOAC methods. Data were subjected to Principal component analysis for classification, ANOVA (5% LSD) and correlation analysis to determine if treatment effects have an influence on weevil infestation. From the plant and seed characteristics evaluated, cowpea seed could be classified into various groups based on skin characteristics; grey mottled, white, light red, red, black, cream, brown mottled. The results also showed that there is significant variation in plant and seed characteristics and these eventually have an influence on cowpea weevil infestation. Large and brightly colored seeds were more infested compared to dark and small seeds. Days to flower and maturity and flower pigmentation had positive correlation with weevil infestation. Lines with high level of protein content were more infested than cowpea lines with low protein content. Lines with high tannin levels (above 0.25) had less infestation compared to those with low tannin content (below 0.05). There was variation with regard to plant and seed characteristics among the cowpea lines studied and these had an influence on the cowpea weevil infestation. This information is important for farmers and breeders selection for cowpea improvement.