Adaptation of cowpea weevil, Callosobruchus maculatus(F), on cowpea and chickpea host plants and comparison of DNA polymorphism by AFLP analysis

In this study, host plant adaptation of cowpea weevil, Callosobruchus maculatus (F.), was investigated on chickpea and cowpea. While molecular studies were conducted by using AFLP technique, biological adaptation was measured thru the number of eggs laid on different legume hosts. Selection based on egg laying preference on chickpea-bean seeds resulted in an increase from 4.98% to 23.09% of chickpea preference after 8 cycles of selection. On the other hand, selection with cowpea-bean seeds at the first cycle of selection was 48.32% and remained at similar levels after 8 cycles of selection (47.72%). After selection studies, three populations, "original" (unselected), "selected toward chickpea", and "selected toward cowpea" were used for biological fitness on several legumes and DNA polymorphism. The results showed that all three populations had similar preference for egg-laying on any given legume seeds tested. The Gst value measured by AFLP technique was 0.046 indicating no differences among populations. The genetic distance matrix values among original and selected populations at different generations were also similar supporting the limited adaptation of egg laying preference toward different legume hosts.