Submitted to: Journal of Applied Entomology
Publication Type: Peer reviewed journal
Publication Acceptance Date: 3/18/2007
Publication Date: 7/2/2007
Citation: Miller, N.J., Ciosi, M., Sappington, T.W., Ratcliffe, S.T., Spencer, J.L., Guillemaud, T. 2007. Genome Scan of Diabrotica virgifera virgifera for Genetic Variation Associated with Crop Rotation Tolerance. Journal of Applied Entomology. 131(6):378-385. Interpretive Summary: The western corn rootworm is a major pest of corn in North America and Europe. Historically, crop rotation has been an effective strategy for avoiding damage by this insect, but a variant has recently evolved that can get around crop rotation by laying its eggs in soybeans. Thus in areas where the variant is present, rootworms will damage first-year corn. The variant arose in east-central Illinois in the early 1990s, and has been spreading through the central U.S. Corn Belt ever since. DNA from samples of rootworms from populations in rotation-susceptible and rotation-resistant regions was compared to search for a DNA marker that could be used to distinguish resistant from susceptible beetles. A marker was found that is associated with rotation-resistance, but it is not completely diagnostic. This study will guide future attempts to find a diagnostic marker, which is important because it would help crop consultants and growers make better decisions for preventing rootworm damage in their cornfields.
Technical Abstract: Crop rotation has been a valuable technique for control of the western corn rootworm, Diabrotica virgifera virgifera, for almost a century. However, during the last two decades, crop rotation has ceased to be effective in an expanding area of the United States Corn Belt. This failure appears to be due to a change in the insect’s oviposition behavior, which, in all probability, has an underlying genetic basis. A preliminary genome scan using 253 Amplified Fragment Length Polymorphism (AFLP) markers sought to identify genetic variation associated with the circumvention of crop rotation. Samples of D. v. virgifera from east central Illinois, where crop rotation is ineffective, were compared to samples from Iowa at locations that the behavioral variant has yet to reach. A single AFLP marker showed signs of having been influenced by selection for the circumvention of crop rotation. However, this marker was not diagnostic. The lack of markers strongly associated with the trait may be due to an insufficient density of marker coverage throughout the genome. A weak but significant general heterogeneity was observed between the Illinois and Iowa samples at microsatellite loci and AFLP markers. This has not been detected in previous population genetic studies of D. v. virgifera and may indicate a reduction in gene flow between variant and wild type beetles.