Interactions between cowpea weevil (Coleoptera: Bruchidae) populations and Vigna (Leguminosae) species

Abstract

The cowpea weevil, Callosobruchus maculatus (F.), cowpea, Vigna unguiculata (L.) Walpers, and wild Vigna species (progenitors of cowpea) have interacted for thousands of generations in Africa. Consequently, cowpea weevil virulence to Vigna species and the resistance within Vigna species to cowpea weevil populations may vary significantly. Given the current interest in using wild Vigna species as sources of cowpea weevil resistance, it is essential to determine the importance of the variation in cowpea weevil and Vigna interactions. To examine cowpea weevil and Vigna interactions, 3 experiments were conducted using 6 cowpea weevil populations and multiple accessions of 4 cowpea weevil-resistant Vigna species. In general, we found significant variation among cowpea weevil populations for virulence to resistant cowpea landrace TVu 2027. Unexpectedly, we found that TVu 2027 was susceptible to a cowpea weevil population from an unknown location in Nigeria. In addition, we found significant variation among accessions within each of the 3 wild Vigna species for resistance to cowpea weevil populations. Considering the potential for low durability of resistance (when using Vigna species as sources of cowpea weevil resistance), coupled with the difficulty of moving cowpea weevil resistance genes from wild Vigna species to domesticated cowpea, it may be more productive to focus on developing a transformation system for cowpea, and search for cowpea weevil resistance genes outside the genus Vigna and outside other genera having species that serve as host plants for the Cowpea weevil.