western corn rootworm Metagenome

The western corn rootworm (WCR), Diabrotica virgifera virgifera Leconte, is the most severe pest of corn in the United States. Damage is commonly managed through transgenic corn plants expressing an entomotoxin (Bt) from the soil bacterium Bacillus thuringiensis. Feeding on Bt proteins disrupts the insect gut membrane, leading to fatal septicemia. However, WCR are capable of evolving resistance to Bt in as little as three generations and have currently evolved resistance to all four Bt toxins on the market. Previous studies have shown that the microbiota is crucial for susceptibility to Bacillus thuringiensis (Bt) in Lepidopteran species, but the specific role has not been investigated in Coleopteran species. Upon damage to the midgut epithelia commensal bacteria present in the gut lumen may gain entry to the hemocoel compartment which may favor opportunistic pathobionts and septicemia. Resistant WCR larvae could be better able to contain pathobiont infection. To test this hypothesis we surveyed microbiota using 16S rRNA amplicon sequencing. We compared associated microbial species of larvae from a resistant WCR colony and a susceptible control colony on three formats (artificial diet, on maize seedlings, and on maize plants) while feeding for 1, 3 and 5 days on Bt-expressing corn or its near-isoline analogue as a control. Identification of bacteria associated with Bt-resistance will aid in the development of new resistance management techniques and technologies.