41st Annual Meeting of the Society for Invertebrate Pathology
and 9th International Conference on Bacillus thuringiensis

The use of transgenic Bt-maize is increasing yearly (last year accounting for about 19% of the total maize planted area in the world) because of the efficient control of the corn borers, in especial Ostrinia nubilalis . Resistance to Bacillus thuringiensis (Bt) insecticidal toxins has been linked to the 12-domain cadherin locus in 3 lepidopteran species. The O. nubilalis cadherin gene has been revealed as a complex gene of about 20 kbp in length, with 34 introns. In the present work, we have studied the size polymorphism of the gene in a Spanish population, by amplifying the genomic sequence of the gene in 16 overlapping regions. The variability observed was not uniformly distributed, with a maximum in region 14 and a minimum (no polymorphism) in region 4. All this size variability must be due to changes in the intronic regions because we found no detectable size differences in mRNA. This variability can be useful to select appropriate polymorphic regions to be used as markers of this gene in experiments such us to determine the genetic linkage of the cadherin to Bt resistance traits.