Mitochondrial Genetic Diversity of Bemisia tabaci (Gennadius) (Hemiptera: Aleyrodidae) Associated with Cassava in Lao PDR

Simple Summary The whitefly species Bemisia tabaci is a known pest of cassava and a vector of cassava geminiviruses in Africa and India, but its role in the recent spread of Cassava Mosaic Disease (CMD) in Southeast Asia is not well known. This is in part due to a lack of data on the occurrence and distribution of B. tabaci in this region. We show here the first results of any country-wide survey and identification of B. tabaci colonizing cassava in Lao PDR. Cassava Mosaic Disease (CMD) caused by Sri Lankan cassava mosaic virus (SLCMV), has rapidly spread in Southeast Asia (SEA) since 2016. Recently it has been documented in Lao PDR. Previous reports have identified whitefly species of B. tabaci as potential vectors of CMD in SEA, but their occurrence and distribution in cassava fields is not well known. We conducted a countrywide survey in Lao PDR for adult whiteflies in cassava fields, and determined the abundance and genetic diversity of the B. tabaci species complex using mitochondrial cytochrome oxidase I (mtCOI) sequencing. In order to expedite the process, PCR amplifications were performed directly on whitefly adults without DNA extraction, and mtCOI sequences obtained using nanopore portable-sequencing technology. Low whitefly abundances and two cryptic species of the B. tabaci complex, Asia II 1 and Asia II 6, were identified. This is the first work on abundance and genetic identification of whiteflies associated with cassava in Lao PDR. This study indicates currently only a secondary role for Asia II in spreading CMD or as a pest. Routine monitoring and transmission studies on Asia II 6 should be carried out to establish its potential role as a vector of SLCMV in this region.

Automated summary

This study investigated the abundance and genetic diversity of whitefly species on cassava fields in Lao PDR. The results showed low abundance of whiteflies, with the presence of two cryptic species of the B. tabaci complex, Asia II 1 and Asia II 6. This study provides important data for understanding the role of whiteflies in the spread of Cassava Mosaic Disease and suggests the need for further monitoring and transmission studies.