Population genetic structure and symbionts of whitefly Trialeurodes vaporariorum and Bemisia tabaci (Hemiptera: Aleyrodidae), in the UK and Iraq

Abstract

Whiteflies are major pests of many crops worldwide. The population structure and symbionts of whitefly species have been studied in different regions, but there is little knowledge about Trialeurodes vaporariorum in the UK and Bemisia tabaci in Iraq. MtCOI sequencing and microsatellite genotyping were used to investigate the population structure and endosymbionts of T. vaporariorum from the UK and B. tabaci from Iraq. The study aimed to answer questions about the occurrence of haplotypes/biotypes, genetic differentiation among populations, identity of symbionts, and if agricultural management might affect their genetic diversity. MtCOI sequencing showed that T. vaporariorum had a low level of variation, with only two mitochondrial haplotypes (mtH) with one nucleotide difference. The results revealed a new record of haplotype mtH3 from Essex and Norfolk in the UK. However, the mtCOI sequencing of B. tabaci suggested a high level of polymorphism, with 31 variable nucleotide sites. Four haplotypes of B. tabaci (B, B2, Unknown, and MEAM2) were identified in Iraq. The genotyping results suggested clustering of T. vaporariorum in the UK which was linked to location, but not to host plant. The population structure suggests that glasshouse agroecosystems restrict gene flow between populations. However, the genotyping of B. tabaci showed low genetic clustering, which was linked to location and time of collection, but not host plant. The results for symbionts showed that all female and male B. tabaci harboured one primary symbiont, Portiera aleyrodidarum, and most (96%) had two secondary symbionts: Hamiltonella sp. and Rickettsia sp. P. aleyrodidarum was detected in both sexes of T. vaporariorum, whereas one secondary symbiont, Arsenophonus sp., was detected in almost all females, but not males. The new haplotypes of B. tabaci might be linked with new strains of plant virus in Iraq. The new mtH3 of T. vaporariorum might be important for growers in the UK. These findings both present challenges and may be opportunities for the improved management of these pests in both countries.