Screening for insecticide resistance in Australian field populations of Bemisia tabaci (Hemiptera: Aleyrodidae) using bioassays and DNA sequencing

Abstract

BACKGROUND Species within the Bemisia tabaci cryptic species complex can cause significant crop damage. We used high-throughput amplicon sequencing to identify the species composition and resistance allele genotypes in field populations from cotton fields in Australia. For selected populations, the resistance phenotype was determined in bioassays and compared to sequencing data. RESULTS A metabarcoding approach was used to analyse the species composition in 144 field populations collected between 2013–2021. Two mixed AUS I and MEAM1 populations were detected while the remaining 142 populations consisted of MEAM1 only. High-throughput sequencing of organophosphate and pyrethroid resistance gene amplicons showed that the organophosphate resistance allele F331W was fixed (>99%) in all MEAM1 populations, while the pyrethroid resistance allele L925I in the voltage-gated sodium channel gene was detected at varying frequencies [1.0–7.0% (43 populations); 27.7% and 42.1% (2 populations); 95–97.5% (3 populations)]. Neither organophosphate nor pyrethroid resistance alleles were detected in the AUS I populations. Pyrethroid bioassays of 85 MEAM1 field-derived populations detected no resistance in 51 populations, while 32 populations showed low frequency resistance, and 2 populations were highly resistant. CONCLUSIONS We demonstrate that high-throughput sequencing and bioassays are complementary approaches. The detection of target site mutations and the phenotypic provides a comprehensive analysis of the low-level resistance to pyrethroids that is present in Australian cotton farms. In contrast, a limited survey of whitefly populations from horticulture found evidence of high-level resistance against pyrethroids. Furthermore, we found that the F331W allele (linked to organophosphate resistance) is ubiquitous in Australian MEAM1. This article is protected by copyright. All rights reserved.