Genetic diversity in vector populations influences the transmission efficiency of an important plant virus

The transmission efficiency of aphid-vectored plant viruses can differ between aphid populations within a given aphid species. Intra-species diversity (genetic variation, endosymbionts) is a key determinant of phenotype in aphid populations; however, it is unclear whether intra-species diversity also explains variation in transmission efficiency between aphid populations. Here, we use multiple populations of two aphid species that vector barley yellow dwarf virus (BYDV), the grain aphid (Sitobion avenae) and the bird cherry-oat aphid (Rhopalosiphum padi), and examine how diversity in vector populations influences virus transmission efficiency. We use Illumina sequencing to characterise genetic and endosymbiont variation in multiple S. avenae and R. padi populations and conduct BYDV transmission experiments to identify links between intra-species diversity in the vector and virus transmission efficiency. We observe limited variation in the transmission efficiency of S. avenae, with transmission efficiency consistently low for this species. However, for R. padi we observe a range of transmission efficiency and show that BYDV transmission efficiency is influenced by genetic diversity within the vector, identifying SNPs that potentially contribute towards variable transmission efficiency in R. padi. Our results represent an important advancement in our understanding of the relationship between genetic diversity, vector-virus interactions, and virus transmission efficiency.