Potato yellow vein virus: its host range, distribution in South America and identification as a crinivirus transmitted by Trialeurodes vaporariorum

Sporadic outbreaks of potato yellow vein disease (PYVD) were first observed in the early 1940's by potato growers in Antioquia, Colombia. Long known to be transmitted by the greenhouse whitefly (Trialeurodes vaporariorum), the precise identity of its causal agent (presumably viral in nature) has remained obscure. Here, we present evidence that a closterovirus with a bipartite genome, potato yellow vein virus (PYVV), is associated with PYVD. Electrophoretic analysis revealed that diseased tissue contains 4–5 disease‐specific dsRNAs ranging in size from c. 9 000–1 800 bp. RT‐PCR reactions containing pairs of degenerate primers directed against conserved motifs in the closterovirus heat‐shock protein homologue produced products of the expected sizes. Comparison of the corresponding amino acid sequences revealed striking similarities between PYVV and two bipartite, whitefly‐transmitted criniviruses, Cucurbit yellow stunting disorder and Tomato chlorosis viruses. Epidemiological surveys carried out in Rionegro, Colombia identified Polygonum mepalense, Polygonum spp., Rumex obtusifolium, Tagetes spp., and Catharanthus roseus as potential viral reservoirs. PYVV is transmitted through tubers, and visual symptoms alone cannot be used to determine infection status. A sensitive hybridisation‐based assay for PYVV has been developed for use in seed certification programmes.