Year: 2005
Type: dissertation
Abstract: The rise of large scale agriculture in the 20 th century created the need for effective strategies to control insect pests.Treatment with chemical insecticides has been a weapon of choice, but the inevitable evolution of resistance has followed in many insect species.Resistance represents a major challenge, not only for agricultural production, but also for environmental preservation and human health.Two major options for resistance have been identified, and these are target-site based and metabolic-based resistance.Much insecticide resistance research focuses on identifying these mechanisms through genetic and molecular analysis.The insecticide lufenuron is the focus of this study.It belongs to a novel insecticidal group called the insect growth regulators, which were introduced in 1970s as highly selective insecticides with low vertebrate toxicity.Resistance to lufenuron in the nonpest species Drosophila melanogaster has been observed in field populations, despite the lack of field usage of lufenuron (Wilson & Cain, 1997;O'Keefe, 1997).This study has taken advantage of this phenomenon to investigate resistance mechanisms in natural populations.At least two detoxification mechanisms were identified.A resistant isofemale strain isolated in Victoria, Australia was used to identify the detoxification gene, Cyp12a4, that may be involved in resistance.Tissue-specific overexpression of this gene appears to confer resistance to lufenuron, as confirmed through the generation and screening of transgenic overexpressing strains.A second mechanism was identified from an isofemale strain isolated from field populations in Coloardo, USA.Another detoxification gene, Cyp6g1, was found to be overexpressed in this strain.Transgenic screening confirms its involvement in conferring resistance to lufenuron.A partial transposon insertion (Accord) was identified, and implicated as the overexpression conferring mutation.An alternate allele containing a partial P-element within Accord was identified in a strain collected from Australian (Queensland) natural populations.The frequency of these alleles is high.Mutagenesis was also used in an attempt to identify the lufenuron target.17 mutants were isolated, and due to an experimental bias, all carried the Cyp6g1 mechanism and another as yet unidentified mechanism on another chromosome.This study highlights the importance of the need for better understanding of insecticide resistance, and particularly, the arsenal of metabolic detoxification mechanisms available to insect pests, as a method of prolonging the effectiveness of insecticides.
Author: Michael Bogwitz
Language: English
Subfield: Molecular Biology
Domain: Life Sciences
SDG: Zero hunger
Open Access status: green
OpenAlex ID: W2581569010