Crop rotation between corn and soybeans is thought to have led to the selection of a new biotype of western corn rootworm, Diabrotica virgifera virgifera LeConte, which lays eggs in soybean fields. In order to identify DNA markers associated with the novel phenotype 210 random amplified polymorphic DNA (RAPD) primers were screened using DNA from individuals of normal and soybean-adapted rootworm. The soybean adapted individuals were collected during emergence from 20 sites in Illinois and one in Indiana, in corn fields that were rotated with soybean in the previous year. The wild-type insects were collected after emergence, from 19 continuous corn fields in western Illinois. More than 200 RAPD bands were scored for 129 individuals including soybean-adapted and wild type WCR biotypes, from 39 sites in Illinois, 1 site in Indiana and sites in south-western Ontario. Samples from 26 northern corn rootworm sites in SW Ontario were included. Eighty-five polymorphic markers between individuals were identified. A dendrogram was constructed using an unweighted pair-group method with arithmetical averages (UPGMA), and a principal coordinates analysis both showed significant clustering of northern, normal and mutant corn rootworms with moderate overlap between normal and mutant corn rootworms. Two bulks of DNA, comprised of individuals from 20 sites, were made from soybean-adapted and wild-type phenotypes. A total of 41 polymorphisms between bulks have been identified. This is the first report of genetic markers associated with this important phenotype. Experiments are underway to confirm the association between these markers and the soybean adaptation behaviour.
Species 1: Coleoptera Chrysomelidae Diabrotica virgifera virgifera (western corn rootworm)
Keywords: soybean adapted WCR biotype, molecular markers
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