Date of Award
Doctor of Philosophy
Daniel F. Voytas
Leslie C. Lewis
A candidate gene approach was taken to characterize Bacillus thuringiensis (Bt) crystalline (Cry) toxin resistance phenotypes of the European corn borer, Ostrinia nubilalis (Hubner), and anonymous genomic markers were used to estimate subpopulation differentiation and migration rates that may affect spread of resistance phenotypes in the North American population. Native and transgenic variants of Bacillus thuringiensis (Bt) crystalline ( Cry) toxins control larval lepidopteran feeding upon important agronomic crop plants. Invertebrate Bt resistance phenotypes arise via altered expression of midgut proteases involved in Cry toxin activation (trypsins) and degradation (chymotrypsins), reduced toxin binding to N-acetylgalactoseamine (GalNAc) modified peptide receptors (cadherin, aminopeptidase, or alkaline phosphatase), or receptor glycosylation pathway knockouts (beta-1,3-galactosyltransferases; beta3GalT5). Ostrinia nubilalis trypsin, chymotrypsin, cadherin, and beta3GalT5 cDNA clones, transcript expression, and partial genomic genomic DNA copies were characterized. Mendelian inheritance of trypsin, chymotrypsin, and cadherin genomic DNA markers suggest association between allele segregation and Bt resistance phenotypes can be conducted. Movement of O. nubilalis moths was indirectly estimated by genetic similarity between North American subpopulations using mitochondrial and genomic microsatellite markers. Marker data suggested differentiation between two O. nubilalis ecotypes, univoltine and bivoltine, which may affect movement of Bt resistance phenotypes in northern regions of the Midwest United States.
Digital Repository @ Iowa State University, http://lib.dr.iastate.edu/
Brad Steven Coates
Coates, Brad Steven, "Genomic markers for the study of Ostrinia nubilalis population dynamics and traits conferring resistance to Bacillus thuringiensis (Bt) crystalline toxins " (2005). Retrospective Theses and Dissertations. 1855.