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Citrus viroid V: Occurrence, Host Range, Diagnosis, and Identification of New Variants

First author: Centro de Protección Vegetal y Biotecnología, Instituto Valenciano de Investigaciones Agrarias, Apartado Oficial, 46113-Moncada, Valencia, Spain; second author: Instituto de Biología Molecular y Celular de Plantas (CSIC-Universidad Politécnica de Valencia), Avenida de los Naranjos s/n, 46022 Valencia, Spain; third and fourth authors: Centro de Protección Vegetal y Biotecnología, Instituto Valenciano de Investigaciones Agrarias, Apartado Oficial, 46113-Moncada, Valencia, Spain; fifth author: Núcleo de Microscopia Eletrônica, Escola Superior de Agricultura Luiz de Queiroz, USP, Piracicaba, Brazil; sixth and seventh authors: Instituto de Biología Molecular y Celular de Plantas (CSIC-Universidad Politécnica de Valencia), Avenida de los Naranjos s/n, 46022 Valencia, Spain; and eighth author: Centro de Protección Vegetal y Biotecnología, Instituto Valenciano de Investigaciones Agrarias, Apartado Oficial, 46113-Moncada, Valencia, Spain.

The recently described Citrus viroid V (CVd-V) has been proposed as a new species of the genus Apscaviroid within the family Pospiviroidae. Analysis of 64 samples from different citrus-growing areas has shown that CVd-V is present in the United States, Spain, Nepal, and the Sultanate of Oman. CVd-V found in six sweet orange sources from the Sultanate of Oman was identical to the reference CVd-V variant, whereas three new variants with sequence identities of 98.6% (CVd-V^CA), 97.3% (CVd-V^ST), and 94.9% (CVd-V^NE) were identified in sources from California, Spain, and Nepal, respectively. These results suggest that this viroid has not emerged recently and that it is relatively widespread. Transmission assays to sweet orange, mandarin, and mandarin hybrids, clementine, satsuma, lemon, sour orange, Tahiti lime, Palestine sweet lime, calamondin, bergamot, and kumquat have shown that all these citrus species and citrus relatives are hosts for CVd-V. Several indexing approaches, including slot blot, northern blot hybridization, and reverse transcription-polymerase chain reaction, have been evaluated for detecting CVd-V, either using Etrog citron as an amplification host or directly from commercial species and cultivars.