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

The cowpea weevil, Callosobruchus maculatus (F.), cowpea, Vigna unguiculata (L.) Walpers, and wild Vigna species (progenitors of cowpea) have interact ed for thousands of generations in Africa. Consequently, cowpea weevil viru lence to Vigna species and the resistance within Vigna species to cowpea we evil populations may vary significantly. Given the current interest in usin g wild Vigna species as sources of cowpea weevil resistance, it is essentia l to determine the importance of the variation in cowpea weevil and Vigna i nteractions. To examine cowpea weevil and Vigna interactions, 3 experiments were conducted using 6 cowpea weevil populations and multiple accessions o f 4 cowpea weevil-resistant Vigna species. In general, we found significant variation among cowpea weevil populations for virulence to resistant cowpe a landrace TVu 2027. Unexpectedly, we found that TVu 2027 was susceptible t o a cowpea weevil population from an unknown location in Nigeria. In additi on, we found significant variation among accessions within each of the 3 wi ld Vigna species for resistance to cowpea weevil populations. Considering t he 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 cow pea, it may be more productive to focus on developing a transformation syst em for cowpea, and search for cowpea weevil resistance genes outside the ge nus Vigna and outside other genera having species that serve as host plants for the cowpea weevil.