Abstract
The management of the olive fruit fly (Bactrocera oleae) is traditionally based upon the use of organophosphate insecticides, mainly dimethoate. In this evolutionary arms race between man and pest, the flies have adapted a pesticide resistance, implying two point-mutations of the Ace gene -I214V and G488S- and a 9bp deletion -Δ3Q. We revisited 11 Iberian locations to evaluate this adaptation of organophosphate (OP)-resistant alleles through amplicon sequencing. Screening for populations where the wild type is prevalent allows an identification of hotspots for targeted mitigation measures; we have hence refined the scale to the region with the lowest OP-resistant alleles frequency 71 locations were sampled and individuals checked using a fast and low-cost allele-specific-primer polymerase chain reaction (ASP-PCR) method]. An increase in Ace gene point-mutations was observed, and the Δ3Q mutation remains undetected. The lowest frequencies of the OP-resistant alleles remain in the west, underlining the hypothesis of an introduction of resistance from eastern Mediterranean areas. A field test was performed by sampling the fly population before and after in-practice dimethoate application. A clear reduction in olive fruit fly numbers was observed, with no relevant changes in the genotypic frequencies of the resistance alleles. The findings are discussed in frame of the type and intensity of the selection pressure that has led to the adaptation to resistance and its consequences from the producer perspective.
Highlights
In the evolutionary arms race [1] against agricultural pests, the intensive use of organophosphates (OPs) in the last 50 years has led to an evolution of resistance
Our results support the previous observation of complete concordance between the zygosities Our results support the previous observation of complete concordance between the zygosities of I214V and G488S in Iberian samples [18], strengthening the suggestion that, in this region, the of I214V and G488S in Iberian samples [18], strengthening the suggestion that, in this region, the
I214V and G488S in Iberian samples [18], strengthening the suggestion that, in this region, the resistance alleles result of a migration event of flies with a chromosome already carrying both substitutions, and are not a result of a local and independent ‘de novo’ origin
Summary
In the evolutionary arms race [1] against agricultural pests, the intensive use of organophosphates (OPs) in the last 50 years has led to an evolution (or adaptation) of resistance. Insensitivity to these insecticides by mutations of the Ace gene, which codes for acetylcholinesterase, the target enzyme of OPs, has been demonstrated in several insects, including mosquito species, in Drosophila melanogaster (common fruit fly), Musca domestica (common housefly), Ceratitis capitata (Mediterranean fruit fly), Aphis gossypii (the aphid) and Bactrocera oleae [2,3,4,5,6]. Resistance can evolve through selection from standing variation or through ‘de novo’ mutations
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