Genetic diversity and population dynamics of whiteflies associated with cassava mosaic disease in Mozambique

Cassava mosaic disease (CMD), caused by a complex of begomoviruses (family Geminiviridae) is the main biotic constraint for cassava cultivation in the African continent. Its spread has been driven by sub-Saharan Africa (SSA) species of whiteflies from the Bemisia tabaci cryptic species complex. However, information on the genetic make-up of whitefly populations is lacking for several African countries where cassava is an important crop, including Mozambique. The aim of this work was to determine the geographic distribution and genetic diversity of whiteflies associated with cassava mosaic disease in Mozambique. A survey was conducted in 2018 in the main cassava production regions. Fourteen districts in five provinces were sampled, and DNA was extracted from 864 individual whiteflies. The prevalence and severity of CMD was also assessed, and the results highlight its wide distribution in all sampled fields. Based on pairwise comparisons and molecular phylogeny of the mitochondrial cytochrome c oxidase subunit I gene (mtCOI), three African B. tabaci putative species were present. Sub-Saharan Africa 1 subgroup 3 (SSA1-SG3) is the most prevalent species, representing 70% of the individuals analyzed. The prevalence of B. tabaci Sub-Saharan Africa 5 (SSA5), and of a putative new species, named B. tabaci Sub-Saharan Africa 21 (SSA21), was of approx. 6%, occurring in most fields. We also detected for the first time the occurrence of B. afer in Mozambique, with 24% prevalence. Our results provide the first comprehensive description of whitefly diversity in cassava crops in Mozambique and underscore the expansion of African whitefly populations.