Species richness, genetic diversity and population structure of the species complex Bemisia tabaci on cassava and associated plants in the CEMAC zone

Abstract

The study of species and genetic richness of crops pest vector of plant viruses in a biological context of invasion in continental environment, is essential for understanding the mechanisms that underlay viral emergencies in sub-Saharan Africa. The cryptic Bemisia tabaci species complex is composed of many species, including the Sub-Saharan group of species that are subservient to cassava in Africa. They are directly involved in the vection of many viruses causing cassava mosaic disease (CMD) or the cassava brown streak diseases (CBSD). These diseases cause severe yield losses in cassava crops, which are among the leading starchy root crops in the African continent. Unfortunately very few studies on the vector of these diseases had been made in numerous African countries where the disease is of great concern. The diversity of whiteflies species on cassava in some countries remains broadly unknown. Furthermore, little information is available on the gene flow within species and between genetic subgroups recently described within these species. It is in this context that we conducted a genetic study on 898 samples from Central Africa and 667 samples from Cameroon using nuclear (microsatellites) and mitochondrial (COI) markers. These analyzes have allowed the characterization of the genetic variability at the intra- and inter-species level. The possible effect of factors such as the host plant and the geographical origin of analyzed individuals, often reported as genetic structuring factors in the species B. tabaci were also tested for (i) determining the nature of the species in circulation in these countries, (ii) understand the distribution of these populations, (iii) assess the extent of their diversity and genetic, structure, and (iii) consider the contribution of this knowledge in the management of whitefly populations in Central Africa. We were able to describe the presence of 6 species of B. tabaci complex and 5 subgroups of a species (SSA1) of th