Resistance to insecticides evolves by natural selection. The number of generations until resistance causes control failures is dependent on the initial allele frequency. Most population genetic models have been based on theoretical estimates of initial allele frequencies because of scanty empirical data. Resistance to Bacillus thuringiensis (Bt) has become of particular concern with the advent of transgenic crops. The initial allele frequency for Bt resistance has become highly controversial with results published in the Proceedings of National Academy of Sciences, USA estimating it as high as 10-3. Since the alleles conferring resistance to Bt are predominantly recessive, we used isofemale lines technique to estimate the frequencies of alleles for Bt resistance in the field populations. This technique increases homozygosity and allows ready detection of recessive alleles. The main objective of this project was to estimate the frequencies of alleles conferring resistance to Bt endotoxins in the field populations of Plutella xylostella, diamondback moth (DBM) because the rate of evolution of resistance is mainly linked to the initial allele frequencies. Our results indicate that the frequencies of alleles conferring resistance to Bt endotoxins in the field populations of DBM are much lower than >10-3. This empirical estimation will allow us to devise better strategies for resistance management of biopesticide, based on Bt endotoxins in general and transgenic crops specifically.
Species 1: Lepidoptera Plutellidae Plutella xylostella (diamondback moth, cabbage moth)
Keywords: Bt, resistance
The ESA 2001 Annual Meeting - 2001: An Entomological Odyssey of ESA