First Report of Tomato spotted wilt virus in Sweet Pepper in Taiwan.

A new disorder on pepper showing symptoms of chlorosis and chlorotic spots on leaves was observed in sweet pepper (Capsicum annuum cv. Andalus) fields in Ren-Ai Township, Nantou County in July, 2009. The disorder occurred in more than 30% of the pepper plants, with a height of approximately 40 cm (1.5 feet), which was approximately one-half the size of the asymptomatic ones. Symptomatic plants bore much smaller fruits with abnormal shapes. Three symptomatic sweet pepper plants were collected and tested for potential viruses. Reverse transcription (RT)-PCR was performed for the detection using three degenerate primer pairs, gL3637/gL4435c for tospoviruses (2), Hrp5/Pot1 for potyviruses (1,3), and Tob-Uni1/Tob-Uni2 for tobamoviruses (4), and specific primers, FJJ2001-7/FJJ2001-8 (5'-TATGTCCATGGACAAATCCGAATCA and 5'-TCTCTGGATCCACGAGTTCAAACTGGGAG) for the coat protein gene of Cucumber mosaic virus (CMV). An 819-nt DNA fragment containing the partial L RNA of tospovirus was amplified from the total RNA isolated from each of these three samples by RT-PCR with primer pair gL3637/gL4435c. One amplified fragment was cloned and sequenced. A homology search in GenBank indicated that the new pepper-infecting virus in Taiwan was Tomato spotted wilt virus (TSWV) since the partial L RNA shared more than 94.5% nucleotide and 98.2% amino acid identity with five TSWV isolates (Accession Nos. AB190813, AB198742, AY070218, D10066, and NC_002052). No DNA fragment was obtained by RT-PCR using primer pairs for CMV, potyviruses, or tobamoviruses. A virus culture (TwPep1) isolated from one of the symptomatic sweet pepper plants was then established in Nicotiana tabacum cv. White Burley and N. benthamiana through triple single-lesion isolation. TWPep1 reacted positively only to the antiserum against TSWV by indirect-ELISA but not to those of Watermelon silver mottle virus, Capsicum chlorosis virus, Tobacco mosaic virus, Tomato mosaic virus, and CMV. Partial L RNA and the full-length nucleocapsid (N) gene of TWPep1 were obtained by RT-PCR with primer pairs gL3637/gL4435c and FJJ2002-74/FJJ2002-75 (5'-GCGCGCGGATCCTAATTTAACTTACARCTGCT 5'-TGCTGCCTCGAGCATACGGTCAAAGCATATAA), respectively. The 819-nt L RNA conserved region of TwPep1 (Accession No. GU222652) shared 94.4 to 97.7% nucleotide and 98.2 to 100% amino acid identity with those available in GenBank. The 777-bp N gene of TwPep1 (Accession No. GU222651) shared 96.7 to 99.1% nucleotide and 97.3 to 99.6% amino acid identity with 37 TSWV isolates available in GenBank. Sequence comparisons indicated that TwPep1 is an isolate of TSWV. TSWV was later detected by RT-PCR in all 10 symptomatic samples of sweet pepper plants collected from five fields in August 2009. To our knowledge, this is the first report of TSWV in sweet pepper in Taiwan. This is also the first demonstration of isolation and characterization of TSWV in Taiwan although TSWV was once detected in lisianthus (Eustoma rusellianum) by RT-PCR (1) but the isolation was not successful then. The occurrence of TSWV in pepper will have a direct economic impact on the important vegetable and floral industry in Taiwan because TSWV reportedly comprises a wide host range. References: (1) C. C. Chen et al. Bot. Stud. 947:369, 2006. (2) F. H. Chu et al. Phytopathology 91:361, 2001. (3) D. Colinet and J. Kummert. J. Virol. Methods 45:149, 1993. (4) B. Letschert et al. J. Virol. Methods 106:1, 2002.