Phylogeography of Organophosphate Resistant ace Alleles in Spanish Olive Fruit Fly Populations: A Mediterranean Perspective in the Global Change Context

Abstract

The olive fruit fly (olf) Bactrocera oleae is the most damaging olive pest. The intensive use of organophosphates (OPs) to control it, led to an increase in resistance in field populations. This study assesses the presence and distribution of three mutations at the ace gene related to target site insensitivity to OPs in Spain. Samples from other Mediterranean countries were included as external references. Resistance-conferring alleles (from exons IV and VII of the ace gene) reached almost an 80% frequency in olf Spanish populations. In total, 62% of them were homozygous (RR/RR), this being more common in eastern mainland Spain. High frequencies of RR/RR individuals were also found in North Mediterranean samples. Conversely, in Tunisia, only sensitive alleles were detected. Finally, the exon X mutation ∆Q3 had an extremely low frequency in all samples. The high frequency of genotype RR/RR in Spain indicates high fitness in an agroecosystem treated with pesticides, in contrast to ∆Q3. At exon IV all flies carried the same haplotype for the allele conferring resistance. The sequence analysis at this exon suggests a unique origin and fast expansion of the resistant allele. These results provide evidence that OPs appropriate use is needed and prompt the search for alternative methods for olf pest control.

Vast Gene Flow among the Spanish Populations of the Pest Bactrocera oleae (Diptera, Tephritidae), Phylogeography of a Metapopulation to Be Controlled and Its Mediterranean Genetic Context

“…These results are relevant for pest management, since the Spanish olive extension covers more than 2.5 million hectares, which could facilitate gene flow and local olf dynamics of decline/recolonisation. Likewise, the adaptive history of the species to long and current local conditions cannot be avoided to improve an efficient pest control [ 53 ].…”

Status of Acetylcholinesterase Mediated Organophosphate Resistance in Cattle Tick, Rhipicephalus Microplus (Acari: Ixodidae)

“…The OP compounds and many other pesticides can bring various unknown detrimental effects after reaching the environment. They can increase pesticide -degrading organisms of the soil selectively and can give the power of cross resistance to various microorganisms to combat a wide range of antibiotics [69,70,71].…”

Current Status of the Main Olive Pests: Useful Integrated Pest Management Strategies and Genetic Tools

“…Currently, pyrethroids, organophosphates, or neonicotinoids are the approved pesticides to control these pests in olive crops [10]. The misuse and abuse of chemical products in recent decades has led to increases in the distribution and frequency of alleles, conferring resistance to these products in natural pest populations in this area, as has been documented [53][54][55][56]. Such occurrences are a sign of insecticide failure.…”

“…Hence, a dramatic increase in the resistance to PYs such as alpha-cypermethrin has been observed in B. oleae populations in Greece, especially in Crete [55,295]. Spanish olive fruit fly populations also have high frequencies of alleles conferring resistance to organophosphate insecticides, as determined by studying mutations at the ace gene [56]. All of this information helps farmers to make better decisions about when to carry out insecticide interventions, as well as the most appropriate ones.…”