Screening of elite cowpea genotypes for bruchid (Callosobruchus rhodensianus) resistance

Abstract

Cowpea (Vigna unguiculata L. Walp) plays a crucial role in in the health of both humans and animals by providing a rich source of protein especially for those in rural developing areas. However, its production is limited because of lack of seeds due to cowpea bruchid investation. Cowpea bruchid Callosobruchus rhodensianus (F.) (Coleoptera: Chrysomelidae) is one of the major pests of stored cowpea seeds, and it can render the seeds useless if not managed. There are various measures to control this pest, one of which is the host plant resistance which is regarded as the most efficient sustainable measure. The objective was to screen ten elite cowpea genotypes obtained from the University of Limpopo germplasm collection for bruchid resistance. The experiment was carried out at the University of Limpopo Plant Production Laboratory. Four pairs of bruchids were infested into batches of ten seeds of each genotype using a completely randomized design (CRD) with six replications and data were collected for 60 days. The variables measured included initial seed weight (g) (ISW), residual seed weight (g) (RSW), seed weight loss (%) (SWL), number of eggs (NE), seed damage (%) (SD), adult emergence (%) (AE), number of days to insect emergence (days) (NIE), total development time (days) (TDT) and mean development time (days) (MDT). Results show that significant differences (P˂0.05) were observed for ISW, RSW, SWL, and MDT; and the findings of this study further indicated a deviation in adult emergence, with a total development time of 39.50-46.50 days. AYT205A, AYT205B, AYT208B, AYT210B, AYT211A, AYT211B, AYT302A, AYT310B and CB-24J’burg exhibited longer developmental periods, which implies that they are promising lines and can be recommended to smallholder farmers with limited access to high-quality storage facilities. It is essential that further research work be done on these genotypes on the mechanisms of resistance and to identify factors responsible for bruchid vulnerability on cowpea.