Molecular Evolution of the Rdl Gene in Insects

EPA Grant Number: U914777
Title: Molecular Evolution of the Rdl Gene in Insects
Investigators: Glueck, Susan B.
Institution: Cornell University
EPA Project Officer: Broadway, Virginia
Project Period: January 1, 1995 through January 1, 1996
Project Amount: $102,000
RFA: STAR Graduate Fellowships (1995) Recipients Lists
Research Category: Academic Fellowships , Ecological Indicators/Assessment/Restoration , Fellowship - Ecology


The objectives of this research project are to: (1) isolate Colorado potato beetle (CPB) clones carrying the dieldrin resistance gene homologous to that in Drosophila and other insects; (2) screen populations of resistant and susceptible strains of the beetle for nucleotide sequence variation as part of a full-scale effort to locate the dieldrin resistance mutation; and (3) determine the nature of its origin and spread.


This project involves research into mechanisms of dieldrin resistance in the Colorado potato beetle (CPB), an economically significant crop pest. A mutation believed responsible for resistance has been located in Drosophila, Tribolium, and several other insects, and occurs in the Rall subunit of the GABAA receptor gene. It is hypothesized that resistance in the CPB has evolved through a similar mechanism. Current research, soon to be completed, will identify the molecular basis of dieldrin resistance in the CPB. This will lead to a two-front plan for future research involving both molecular biology and insect breeding. Insects will be collected for use in experiments to determine the Mendelian genetics of dieldrin resistance and as a source of genomic DNA. Molecular research will further characterize the nature of dieldrin resistance at the DNA sequence level. Data obtained from this process will help determine whether the resistance mutation arose multiple times in each population under selection or instead arose once and spread through migration.

The CPB, Leptinotarsa decemlineata, is an economically significant and widespread crop pest in the United States, which has rapidly developed resistance to almost every pesticide applied against it, including the cyclodiene insecticide dieldrin (Hare, 1990). Research that explains the mechanism for past evolution of resistance may suggest ways to design more effective pesticides and insect pest management programs. At the same time, the potato beetle, like Drosophila, is a good system in which to study population genetics and evolution of a genetic trait because the causes of selection are well understood. Because similar research is being carried out on Drosophila and other insects, data from the potato beetle will allow for a comparison of the means by which resistance spreads through populations of these organisms. Such a comparison can answer questions about the limitations of insect response to selection induced by humans.

By 1960, the CPB had attained widespread resistance to the previously successful chemical dieldrin, a type of cyclodiene insecticide (Gauthier, 1981). The fruit fly Drosophila melanogaster, while not a crop pest, is ubiquitous in fields where dieldrin has been applied and also has developed resistance to the pesticide. Efforts currently are underway to understand both the mechanism of dieldrin resistance in Drosophila and the means by which it has become entrenched in populations worldwide.

Supplemental Keywords:

fellowship, Colorado potato beetle, dieldrin resistance gene, crop pest, insect, resistance mutation., RFA, Scientific Discipline, Ecosystem Protection/Environmental Exposure & Risk, Monitoring/Modeling, Environmental Microbiology, Biology, environmental monitoring, crop pest insects, environmental impact, molecular monitoring, pesticide resistance gene, biochemistry, genotypes