|HAMMACK, LESLIE - Retired ARS Employee|
|TALLAMY, DOUGLAS - University Of Delaware|
Submitted to: Insects
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 9/8/2015
Publication Date: 11/10/2015
Citation: French, B.W., Hammack, L., Tallamy, D.W. Mating success, longevity, and fertility of Diabrotica virgifera virgifera LeConte (Chrysomelidae: Coleoptera) in relation to body size and Cry3Bb1 resistant and susceptible genotypes. Insects. 2015, 6, 943-960; doi:10.3390/insects6040943.
Interpretive Summary: Western corn rootworm resistance to population control tactics is a widespread problem, with the development of effective resistance management programs often dependent on detailed knowledge regarding the biology associated with resistance evolution. In mating trials pairing virgin Bt resistant and susceptible males and females, we found little impact of Bt resistance on mating success and mating behavior. The number and quality of eggs laid among mated females were similar regardless of Bt resistance and susceptibility. When female longevity was based on male genotype, however, females mated to Bt resistant males had reduced longevity compared to females mated to susceptible males. This could be highly favorable with higher dose toxins if reduced longevity correlates with reduced fitness. Our results help support the theory of refuge beetles emerging from non-Bt corn and mating with beetles emerging from Bt corn to keep resistance low. However, females also preferred to mate with males of similar body weights, which could promote mating among like genotypes if male and female body sizes are affected equally by the currently available higher dose toxins used in corn. Additional knowledge gained by rearing beetles under more natural conditions could reveal subtle differences in their reproductive biology that could help explain the rapid expansion of Bt resistance and develop new strategies to prevent resistance to other, more potent toxins.
Technical Abstract: Insect resistance to population control methodologies is a widespread problem, with the development of effective resistance management programs often dependent on detailed knowledge regarding the biology of individual species and changes in that biology associated with resistance evolution. This study examined the reproductive behavior and biology of western corn rootworm beetles of known body size from lines resistant and susceptible to the Cry3Bb1 protein toxin expressed in Bt maize. In crosses between and within the resistant and susceptible genotypes, no differences occurred in mating frequency, copulation duration, courtship duration, or fertility; however, females mated with resistant males showed reduced longevity. Mating success did not depend on the body size of either males or females, but larger females laid more eggs. A highly significant, moderately strong, positive correlation was found between the body sizes of successfully mated males and females; however, a barely significant, weak correlation also existed for pairs that did not mate.