Submitted to: Journal of Economic Entomology
Publication Type: Peer reviewed journal
Publication Acceptance Date: 7/30/2010
Publication Date: 12/15/2010
Citation: Bernklau, E.J., Bjostad, L.B., Hibbard, B.E. 2010. Antixenosis in maize reduces feeding by western corn rootworm larvae (Coleoptera: Chrysomelidae). Journal of Economic Entomology. 103:2052-2060. Interpretive Summary: The western corn rootworm (WCR) is a major insect pest in continuous corn production. By feeding on corn roots, WCR causes economic losses due to plant lodging and decreased nutrient uptake, both resulting in yield loss. Currently, insecticides and transgenic corn are the only available options for its control under continuous corn production. Seven maize cultivars with natural resistance to WCR developed previously were evaluated in a series of behavioral studies to determine the role of behavior, if any, in their resistance to WCR. In bioassays with cut roots, no larvae entered the roots of the resistant variety SUM2162, but at least 75% of the larvae entered the roots of every other maize type. This is the first known example of a naturally-occurring maize genotype with behavioral resistance to western corn rootworm larval feeding. The six other genotypes also offer sources of native resistance to WCR larval feeding with other mechanisms of resistance and all are potential sources of native resistance to WCR for transfer of desired resistance genes into high yielding commercial varieties.
Technical Abstract: The first known example of a naturally-occurring maize genotype with behavioral resistance to western corn rootworm larval feeding was discovered in tests with SUM2162. Behavioral responses of neonate western corn rootworm (Diabrotica virgifera virgifera LeConte) larvae were evaluated in laboratory bioassays with seven maize (Zea mays L.) genotypes selected for native resistance to rootworm feeding damage. Two susceptible maize genotypes and one transgenic (Bt) maize genotype were included as controls. In soil bioassays with cut roots, no larvae entered the roots of the resistant variety SUM2162, but at least 75% of the larvae entered the roots of every other maize type. Larvae made significantly (P < 0.05) fewer feeding holes in the roots of SUM2162 than in all the other maize genotypes, except the isoline control. In feeding bioassays, larval feeding varied significantly among maize genotypes, but there was no significant difference between the resistant varieties and the susceptible controls. There were no significant differences among any of the genotypes in host recognition (search) behavior of larvae after exposure to the roots.