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Polyvalent Degenerate Oligonucleotides Reverse Transcription-Polymerase Chain Reaction: A Polyvalent Detection and Characterization Tool for Trichoviruses, Capilloviruses, and Foveaviruses

First, second, fourth, fifth, and sixth authors: Equipe de Virologie, UMR GD2P, IBVM, INRA and University Victor Ségalen Bordeaux2, BP81, 33883 Villenave d'Ornon Cedex, France; and third author: Laboratoire de Virologie, Ctifl, Centre de Lanxade, BP21, 24130 La Force, France

A polyvalent nested reverse transcription-polymerase chain reaction (RT-PCR) test using degenerate primers containing inosine (polyvalent degenerate oligonucleotides [PDO]) was developed for filamentous fruit tree viruses belonging to the genera Trichovirus, Capillovirus, and Foveavirus. The 362-bp product was amplified from nucleic acid extracts obtained from Prunus and Malus leaf samples. All the viruses targeted were detected, demonstrating the polyvalence of the test. The variability of a collection of Apple chlorotic leaf spot virus isolates was analyzed using the sequence of the PDO RT-PCR amplified cDNAs. The technique was also used to screen stone fruit materials infected with known agents or with virus-like graft-transmissible diseases of unknown etiology. The results obtained further validated the broad specificity of the assay, with positive amplification obtained for uncharacterized or partially characterized viruses associated with cherry and peach disorders. Sequencing the amplified PCR products either directly or after cloning allowed the identification of variants of known agents and the tentative identification of two new agents, a Trichovirus and a Foveavirus. In addition, sequence comparisons demonstrated that the sequence of the targeted region is phylogenetically informative and of predictive taxonomic value.