Low genetic variability in Bemisia tabaci MEAM1 populations within farmscapes of Georgia, USA

Authors: GAUTAM, SAURABH - University Of Georgia; CROSSLEY, MICHAEL - University Of Georgia; DUTTA, BHABESH - University Of Georgia; COOLONG, TIMOTHY - University Of Georgia; Simmons, Alvin; DA SILVA, ANDRE - University Of Georgia; SNYDER, WILLIAM - University Of Georgia; SRINIVASAN, RAJAGOPALBABU - University Of Georgia

Submitted to: Insects
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/24/2020
Publication Date: 11/26/2020
Citation: Gautam, S., Crossley, M.S., Dutta, B., Coolong, T., Simmons, A.M., Da Silva, A., Snyder, W., Srinivasan, R. 2020. Low genetic variability in Bemisia tabaci MEAM1 populations within farmscapes of Georgia, USA. Insects. 11:834.
DOI: https://doi.org/10.3390/insects11120834

Interpretive Summary: The sweetpotato whitefly is a serious pest of many agricultural crops worldwide. Many studies have examined the genetic structure of whitefly populations separated by geographical barriers. However, very few studies have assessed the population structure of the sweetpotato whitefly at a farmscape level. A farmscape in this study is defined as a habitat with crop and non-crop areas spanning about 5 square miles. By assessing the genetics of 35 populations of whiteflies across farmscapes in Georgia, this study indicates the whiteflies are similar in orgin. This information helps scientists understand the annual whitefly population explosions and subsequent dispersals in the southeast region.

Technical Abstract: Bemisia tabaci is a whitefly cryptic-species complex comprising important phloem feeding insect pests and plant-virus vectors of many agricultural crops. Middle East-Asia Minor 1 (MEAM1) and Mediterranean (MED) are the two most invasive members of the B. tabaci cryptic species complex worldwide. The diversity of agroecosystems invaded by B. tabaci could potentially influence their population structure, but this has not been assessed at a farmscape level. A farmscape in this study is defined as heterogenous habitat with crop and non-crop areas spanning 8 square km. These heterogenous landscapes are ideal for a polyphagous insect like B. tabaci, which can colonize both crop and non-crop habitats. In this study, mitochondrial COI gene (mtCOI) sequences and a set of six microsatellite markers were used to examine the population structure of B. tabaci MEAM1 colonizing different plant species at a farmscape level in Georgia, United States. Thirty-five populations of adult whiteflies on row and vegetable crops and weeds across major agricultural regions of Georgia were collected from fifteen farmscapes with each spanning ~ 8 square km. Surveyed farmscapes were at least 16 km apart. Species identity of collected individuals was confirmed using morphological features and mtCOI sequence analysis. A total of five species/cryptic species of whiteflies (B. tabaci MEAM1, B. tabaci MED, Dialeurodes citri, Trialeurodes abutiloneus, Trialeurodes vaporariorum) were collected and identified. Analysis of 102 mtCOI sequences revealed the presence of a single B. tabaci MEAM1 haplotype across farmscapes in Georgia. Population genetics analyses (AMOVA, PCA and STRUCTURE) of B. tabaci MEAM1 revealed only minimal genetic differences among collected populations in each farmscape and across farmscapes. Overall, our results indicate a high level of gene flow among B. tabaci MEAM1 populations across all sampled farmscapes. Repetitive explosions of whitefly populations driven by a single or a few major whitefly-suitable hosts planted on a wide spatial scale may be the key factor behind the presence of a single panmictic population over the farmscapes of Georgia. These population structuring effects essentially could have important implications for B. tabaci MEAM1 management.