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 t o be transmitted by the greenhouse whitefly (Trialeurodes vaporariorum), th e precise identity of its causal agent (presumably viral in nature) has rem ained obscure. Here, we present evidence that a closterovirus with a bipart ite genome, potato yellow vein virus (PYVV), is associated with PYVD. Elect rophoretic analysis revealed that diseased tissue contains 4-5 disease-spec ific dsRNAs ranging in size from c. 9 000-1 800 bp. RT-PCR reactions contai ning pairs of degenerate primers directed against conserved motifs in the c losterovirus heat-shock protein homologue produced products of the expected sizes. Comparison of the corresponding amino acid sequences revealed strik ing similarities between PYVV and two bipartite, whitefly-transmitted crini viruses, Cucurbit yellow stunting disorder and Tomato chlorosis viruses. Ep idemiological surveys carried out in Rionegro, Colombia identified Polygenu m mepalense, Polygonum spp., Rumex obtusifolium, Tagetes spp., and Catharan thus roseus as potential viral reservoirs. PYVV is transmitted through tube rs, 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.