Characterization of a pea streak virus (PeSV) isolate from Idaho: Evaluation of risks to cool season food legume production in the Pacific Northwest and development of diagnostic tools

Pea streak virus (PeSV) is an aphid-transmitted virus infecting a broad range of legumes, including alfalfa and cool season food legumes such as chickpeas, lentils, and peas. The diseases caused by PeSV in cool season food legumes were studied in the Pacific Northwest (PNW) of the U.S. in the past, prior to the availability of molecular tools and currently the genetic diversity of PeSV in the PNW is largely unknown. To fill in this knowledge gap and evaluate risks posed by main genetic variants of PeSV circulating in the PNW pulses, an isolate of PeSV was collected from alfalfa in Idaho and subjected to molecular and biological characterization on several major cool-season food legume species grown in the PNW, including chickpeas, lentils, and peas. This Idaho isolate of PeSV, PeSV-Id, induced severe necrotic symptoms in chickpeas, lentils, and dry peas, with a mortality reaching 100% in some chickpea lines. The virus was purified and used as an antigen for production of PeSV-specific antibodies, and development of a sensitive ELISA assay. Phylogenetically, PeSV-Id belonged to a tight lineage of North American isolates of the virus, distinct from the alfalfa latent virus strain of PeSV. The virus was easily transmitted mechanically under greenhouse conditions and was found to spread quickly in alfalfa in the field in the span of 3 to 52 months post-planting. Based on the data obtained, PeSV should be considered a potential threat to the production of pulse crops growing in the vicinity of alfalfa.