Due to the recent pesticide ban in Europe, crops are suffering from the diseases caused by insect transmitted viruses. In particular, aphid-borne Pea Enation Mosaic Virus (PEMV) causes serious yield loss in pea (Pisum sativum), an important source of protein. Although some PEMV resistant pea genotypes were identified, resistance genes are not cloned, and the infection process and the mechanisms of symptom development are not understood at a molecular level. Recently, Partner 1 has screened a collection of 240 Pisum genotypes, conducted Genome Wide Association Study (GWAS) and identified a locus involved in quantitative resistance to the pea aphid, Acyrthosiphon pisum, a major pest of pea and the vector of PEMV. There was no strong-effect resistance gene that prevents the aphid to feed on peas, hence the aphid can inoculate the virus to all the genotypes. To identify pea genes that are involved in PEMV transmission, within-host propagation and symptom development, we propose to screen the collection of 240 pea genotypes, completed with some known PEMV resistant and susceptible genotypes, for partial or total resistance against PEMV. We will evaluate PEMV spread and symptom development after aphid inoculation and conduct several GWAS to identify pea genes involved in the resistance to different steps of the infection process. In the same time, we will evaluate the virus induced changes in pea biology using transcriptomics and also in aphid-plant interactions by monitoring aphid performances and feeding behaviour. The identified genes and pathways involved in virus infection and pea-virus-aphid interactions will be examined by functional analyses. The project will identify multiple genes that are involved in virus infection and contributes to understand the mechanisms of viral infection including transmission and its effect on plant-aphid interactions.