Location: Corn Insects and Crop Genetics Research
Project Number: 3625-22000-016-00
Start Date: Oct 01, 2005
End Date: Sep 30, 2010
A combination of methods including classical genetics and molecular techniques will determine what regions of the European corn borer (ECB) genome are associated with resistance to Bacillus thuringiensis (Bt) proteins. Three resistant colonies will be crossed to a susceptible colony; subsequent F2 segregating populations will be analyzed for significant linkage relationships between phenotypes and genetic markers/candidate genes. A major unknown with resistance monitoring methods that rely on the mass mating of field-collected individuals is whether eggs collected from these mating arenas are a representative genetic sample of the collected populations. Best strategy to sample from mass mating arenas will be investigated to better ensure the adequate representation of the genetic variation present in the original field-collected individuals. ECB moths (>100 per location) will be sampled at 80 km intervals along two perpendicular 720-km transects centered in Iowa. In addition to the 80-km scale sampling, an additional eight sites will be distributed along two different parts of the transects, breaking each of two 80-km intervals into five 16-km intervals. This hierarchical design will provide a wide range of distances for sampling the first year. Genetic variation in microsatellite and RFLP molecular markers will be used to determine genetic differentiation and estimate gene flow among locations. Western corn rootworm (WCR) have been sampled from 10 widely separated locations. At least 50 individuals from each location will be genotyped at 10 microsatellite loci. A mark-release-recapture strategy will be used to examine spatial fidelity of newly emerged ECB adults to their natal fields when presented with adjacent areas of grass (cereal crop) suitable as action sites. Careful selection of representative taxa for non-target field studies is a fundamental need. Goals of selection are to choose taxa that effectively represent the invertebrate community while also providing the best chance of detecting any unanticipated effects of Bt crops. Diversity, abundance, functional importance, and exposure or susceptibility to Cry toxins will influence the choice of representative taxa. Bioassays will be conducted using both N. pyrausta-infected and non-infected neonatal larvae susceptible to Bt, and N. pyrausta infected and non-infected neonatal larvae with partial resistance to Bt. The assay regime will expose these insects to laboratory diets containing discriminating amounts of Bt-corn leaf tissue. Controlled experiments in replicated Bt/nonBt strip plots will be used to correlate the level of damage in a nonBt strip of corn to strength of the signal in the yield map data. Our data also will be used to quantify spatial scaling effects on levels of statistical noise and signal strength, and guide design of computational methodology for mapping natural damage in large-scale field experiments. BL-1; Recertified and valid through April 14, 2011.