Aphid vectors impose a major bottleneck on Soybean dwarf virus populations for horizontal transmission in soybean

Many RNA viruses have genetically diverse populations in a single host. Important biological characteristics may be related to the levels of diversity, including adaptability, host specificity, and host range. Shifting the virus between hosts might result in a change in the levels of diversity associated with the new host. The level of genetic diversity for these viruses is related to host, vector and virus interactions, and understanding these interactions may facilitate the prediction and prevention of emerging viral diseases. It is known that luteoviruses have a very specific interaction with aphid vectors. Previous studies suggested that there may be a tradeoff effect between the viral adaptation and aphid transmission when Soybean dwarf virus (SbDV) was transmitted into new plant hosts by aphid vectors. In this study, virus titers in different aphid vectors and the levels of population diversity of SbDV in different plant hosts were examined during multiple sequential aphid transmission assays. The diversity of SbDV populations revealed biases for particular types of substitutions and for regions of the genome that may incur mutations among different hosts. Our results suggest that the selection on SbDV in soybean was probably leading to reduced efficiency of virus recognition in the aphid which would inhibit movement of SbDV through vector tissues known to regulate the specificity relationship between aphid and virus in many systems.