Genetic diversity of thrips populations on Allium species around the world

Abstract

Thrips are a serious pest in many crops. In onion cultivation, Thrips tabaci is the most important, but not the only thrips species causing damage. We investigated which thrips species affects onion and related species worldwide, how much genetic variation there is within T. tabaci populations, and how this evolves. Furthermore, we determined the reproductive mode and the correlation between the genetic and geographic distances. Thrips samples from infested onions or related species were obtained from 14 different locations worldwide. Species and haplotypes were determined through DNA barcoding with the mitochondrial Cytochrome Oxidase subunit I (COI) gene. Thrips tabaci was the most commonly observed species, but Scirtothrips dorsalis, Thrips palmi, Frankliniella intonsa, Frankliniella occidentalis and Frankliniella tenuicornis were also found, especially at the beginning of the growing seasons and depending on the location. The Nei’s genetic distance within T. tabaci was less than 5% and the haplotypes were clustered into two phylogenetic groups, each linked to a specific mode of reproduction, thelytokous or arrhenotokous. Thelytokous thrips were more common and more widely distributed than arrhenotokous thrips. A high percentage of heteroplasmy was detected in the arrhenotokous group. Heteroplasmic thrips were only found in populations where thelytokous and arrhenotokous were present in sympatry. Some T. tabaci haplotypes were present in high frequency at several sampled locations. No correlation was found between the genetic and geographic distances, which points to anthropic activities spreading thrips haplotypes throughout the world.

Phylogenetic and population genetic analyses of Thrips tabaci Lindeman (Thysanoptera: Thripidae) on Allium host in India

“…These results are also consistent with those of molecular phylogeny, which indicate that geographical proximity cannot be used to measure molecular evolutionary patterns in mtCOI. Recent investigations in T. tabaci populations inhabiting on Alliums did not determine any correlations between the genetic and geographic distances ( Li et al, 2020 ; Porta et al, 2023 ). The haplotype networks showed that Group A comprised eight haplotypes, with 307_Himachal Pradesh and 303_Haryana as the most distant haplotypes.…”

“…Nucleotide sequences of mtCOI gene were used for population genetics analysis of onion thrips from eight regions in India. This helped characterise species diversity, geographical distribution of a species, and tracing the phylogeographic origin ( Lombaert et al, 2014 ; Porta et al, 2023 ). In contemporary literature, only 28 haplotypes of mtCOI gene of T. tabaci have been reported worldwide, including Asia, Europe, Australia, America and other 23 countries, and these haplotypes were retrieved from nearly 282 nucleotide sequences ( Iftikhar et al, 2016 ).…”

“…Among these, the onion thrips, Thrips tabaci Lind, is an important pest that costs significant economic losses to various crops every year ( De Kogel et al, 2015 ). Although many thrips have been reported in Alliums, T. tabaci is most commonly observed ( Porta et al, 2023 ). In addition to direct damage to the crop, this insect serves as a vector of two devastating viruses, Iris Yellow Spot Virus (IYSV) and Tomato Spotted Wilt Virus (TSWV) ( Komondy et al, 2024 ; Nachappa et al, 2020 ).…”

“…The genetic variation within this species positively influences their adaptability under diverse climatic conditions. This genetic variation is also linked to their reproductive modes, such as thelytoky, arrhenotoky, and deuterotoky ( Kobayashi & Hasegawa, 2012 ; Nault et al, 2006 ; Gawande et al, 2017 ; Porta et al, 2023 ), as well as vector competence ( Jacobson & Kennedy, 2013 ).…”

“…Its importance in quick and reliable species identification has been widely acknowledged in a numerous taxa worldwide ( International Barcode of Life Consortium, 2023 ). This method has also been applied for thrips identification, diversity analysis ( Bravo-Pérez et al, 2018 ), phylogenetic analysis ( Gawande et al, 2017 ), population structure ( Porta et al, 2023 ), and invasive genetics ( Tyagi et al, 2017 ).…”