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First Report of Tomato spotted wilt virus on Coprosma repens (Mirror Bush) in Italy

Coprosma repens A. Rich. (mirror bush, Rubiaceae) is a hardy salt tolerant shrub that is native to New Zealand where it is primarily a coastal weed. In temperate climates, many variegated varieties and hybrids of mirror bush grow extensively in gardens. In February 2007, irregular or semicircular necrotic spots, sometimes in concentric rings, were noticed on leaves of approximately 2,000 potted, 1-year-old plants of C. repens ‘Tapuata Gold’ obtained as cuttings from a nursery located in Catania Province. The symptoms were detected on approximately 60% of the plants and were localized exclusively on older leaves especially in the yellow or white border. Protein A sandwich (PAS)-ELISA showed mirror bush was positive for the Batavian lettuce strain of Tomato spotted wilt virus (antiserum to TSWV: PVAS-450 from American Type Culture Collection, Manassas, VA). Double antibody sandwich (DAS)-ELISA with polyclonal antisera to Cucumber mosaic virus, TSWV, and Impatiens necrotic spot virus confirmed the presence of only TSWV. Reverse transcription (RT)-PCR was employed to characterize the TSWV isolate. RT-PCR was carried out with primers (forward 5′-TTA ACT TAC AGC TGC TTT-3′ and reverse 5′-CAA AGC ATA TAA GAA CTT-3′) specific for the CP gene of TSWV (3). Amplification was performed in a thermal cycler (Gene Amp PCR System 24000; Perkin Elmer, Hayward, CA) by preheating at 94°C for 5 min followed by 30 cycles of 1.5 min of denaturation at 94°C, 2 min of annealing at 48°C, and 1 min for extension at 72°C. Finally, the amplified DNA was incubated at 72°C for 7 min for a final extension. All samples yielded DNA fragments of the expected size of 823 bp, which included the entire N gene. Purified PCR products were cloned and sequencing (GenBank Accession No. EU020104) was done by Sequiserve (Vatterstetten, Germany). Comparison with sequences available from the GenBank database showed 96 to 99% homology with the same region of the genome for all TSWV isolates, thus confirming the identity of the virus as an isolate of TSWV. In the Rubiaceae family, TSWV was previously detected on Galium spp., Ixora spp., Gardenia jasminoides Ellis, and Bouvardia sp. (1,2,4). To our knowledge, this is the first occurrence of this virus on a member of the genus Coprosma. The high incidence of the disease in the nursery could be due to propagation of cuttings from an infected source.

References: (1) M. K. Hausbeck et al. Plant Dis. 76:795, 1992. (2) C. Jordá et al. Plant Dis. 79:358, 1995. (3) R. A. Mumford et al. J. Virol. Methods 46:303, 1994. (4) A. M. Vaira et al. Plant Pathol. 42:530,1993.