Detection of a tomato strain of Parietaria mottle virus (PMoV-T) by molecular hybridization and RT-PCR in field samples from north-eastern Spain

Parietaria mottle virus (PMoV-T) infecting tomatoes from different commercial fields in Catalonia, Spain was detected by dot-blot and tissue-printing hybridization and one-step reverse transcriptase PCR (RT-PCR). Specific cDNA was amplified by RT-PCR from mechanically infected Chenopodium quinoa plants and cloned into a plasmid vector. A digoxigenin-labelled riboprobe was synthesized for molecular hybridization, and a specific set of primers (PMoV-1F/PMoV-1R) were designed for one-step RT-PCR assays. Material from different parts of PMoV-T-infected tomato plants was used for the analysis. The virus was detected on necrotic apical shoots, fruits with symptoms, and symptomless shoots grown from old necrotic branches, but not on the old necrotic branches themselves. Both molecular hybridization and one-step RT-PCR procedures were highly specific, and no cross-reactions were observed with other related ilarviruses. PMoV-T was detected successfully by molecular techniques on all infected tomato plants collected from commercial fields, although one-step RT-PCR was less robust than molecular hybridization. The observed reliability of tissue-printing hybridization could greatly facilitate both the large-scale analysis and epidemiological studies of this important pathogen.