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Occurrence of Lily mottle virus on Lilium in Italy

Lily mottle virus (LMoV), a member of the genus Potyvirus, is one of the main viruses infecting lily. Symptoms on lily differ according to the susceptibility and sensitivity of different cultivars and hybrids. They range from leaf mottle or mosaic, vein clearing, chlorotic and yellow streaking, leaf curling, and necrotic spots, to milder forms of leaf symptoms. Plants may even be symptomless at some stages of growth. A varietal collection of Lilium from the early 1990s is held in Pistoia Province (Tuscany, Italy) and is composed of Asian hybrids obtained from intraspecific breeding of commercial cultivars. During a survey conducted from May to June 2010, several plants showing vein clearing, leaf mottle, leaf mosaic, and reddish brownish necrotic spots were observed. Leaf samples from 60 symptomatic or symptomless lily plants, belonging to 20 cultivars, were collected and tested for the presence of LMoV. Samples were assayed by double-antibody sandwich (DAS)-ELISA and eight of them, belonging to four different cultivars, tested positive. Total RNA was extracted from 2 g of leaf tissue of every collected sample according to the protocol described earlier (3) and cDNA synthesis was performed with an iScript cDNA Synthesis Kit (Bio-Rad, Hercules, CA). Samples were tested by reverse transcription (RT)-PCR and real-time PCR assays using primers LMoV1 (5′-GCAAATGAGACACTCAATGCTG-3′) and LMoV2 (5′-CGTGCGTGAAGTAACTTCATAG-3′) designed to amplify 651 bp of the coat protein (CP) gene of LMoV (1). Results obtained with RT-PCR and real-time PCR exactly matched those achieved with ELISA assay, and the eight positive samples showed amplicons of the expected size. PCR products from five infected samples were directly sequenced from both directions and submitted in GenBank (Accessions Nos. JQ655106 to JQ655110). Our isolates share more than 99% nucleotide identity among each other. Comparison with other LMoV-CP gene sequences present in GenBank showed nucleotide identities ranging from 93 to 94% with LMoV isolates from South Korea (GenBank Accession Nos. GQ150683 to GQ150686), China (GenBank Accession Nos. EU348826, AJ748256, AJ564636, and AJ564637), Australia (GenBank Accession No. JN127341), and Japan (GenBank Accession No. AB570195). To our knowledge, this is the first report of LMoV on Lilium in Italy where this virus was already reported to infect escarole (2). Considering the economic importance of Lilium production as a flowering plant in Pistoia Province, and in several other areas of Italy, the report of LMoV present on lilies suggests the use of healthy propagation material and the adoption of preventive measures to avoid its diffusion.

References: (1) J.-H. Lim et al. Korean J. Microbiol. 45:251, 2009. (2) V. Lisa et al. Plant Dis. 86:329, 2002. (3) D. J. MacKenzie et al. Plant Dis. 81:222, 1997.