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The virus isolate 2009-GZT, collected from tomato in Guizhou province of China, was identified as a new member of the genus Tospovirus based on its S RNA sequence. Because its provisional name, "tomato necrotic spot virus" (TNSV), was identical to an already existing member of the genus Ilarvirus, 2009-GZT was renamed "tomato necrotic spot-associated virus" (TNSaV). In this study, the full-length sequences of the genomic M and L RNAs of TNSaV were determined and analyzed. The M RNA has 4,773 nucleotides (nt), encoding the NSm protein of 309 aa (34.4 kDa) in the viral (v) strand and the glycoprotein precursor (Gn/Gc) of 1123 aa (128 kDa) in the viral complementary (vc) strand. The NSm and Gn/Gc of TNSaV share the highest aa sequence identity (86.2 % and 86.9 %, respectively) with those of tomato zonate spot virus. The L RNA contains 8,908 nt and codes for the putative RNA-dependent RNA polymerase (RdRp) of 2885 aa (332 kDa) in the vc strand. The RdRp of TNSaV shares the highest aa sequence identity (85.2 %) with that of calla lily chlorotic spot virus (CCSV). Serological assays showed that TNSaV cross-reacts with rabbit antisera against watermelon silver mottle virus (WSMoV) NP and CCSV NP, indicating that TNSaV is a member of the WSMoV serogroup.

Background: Emerging tospoviruses cause significant yield losses and quality reduction in vegetables, ornamentals, and legumes throughout the world. So far, eight tospoviruses were reported in China. Tomato fruits displaying necrotic and concentric ringspot symptoms were found in Guizhou province of southwest China. Finding: ELISA experiments showed that crude saps of the diseased tomato fruit samples reacted with antiserum against Tomato zonate spot virus (TZSV). Electron microscopy detected presence of quasi-spherical, enveloped particles of 80–100 nm in such saps. The putative virus isolate was designated 2009-GZT. Mechanical back-inoculation showed that 2009-GZT could infect systemically some solanaceous crop and non-crop plants including Capiscum annuum, Datura stramonium, Nicotiana benthamiana, N. rustica, N. tabacum and Solanum lycopersicum. The 3012 nt full-length sequence of 2009-GZT S RNA shared 68.2% nt identity with that of Calla lily chlorotic spot virus (CCSV), the highest among all compared viruses. This RNA was predicted to encode a non-structural protein (NSs) (459 aa, 51.7 kDa) and a nucleocapsid protein (N) (278 aa, 30.3 kDa). The N protein shared 85.8% amino acid identity with that of CCSV. The NSs protein shared 82.7% amino acid identity with that of Tomato zonate spot virus(TZSV). Conclusion: Our results indicate that the isolate 2009-GZT is a new species of Tospovirus, which is named Tomato necrotic spot virus (TNSV). This finding suggests that a detailed survey in China is warranted to further understand the occurrence and distribution of tospoviruses.

An isolate of a new tospovirus species, causing concentric zoned ringspots on fruits and necrotic lesions on leaves of infected plants, was characterised based on particle morphology, host range and serological properties. The complete nucleotide sequences of large (L), medium (M), and small (S) RNAs of this virus were found to contain 8919, 4945, and 3279 nts respectively. The L RNA encoded the RNA-dependent RNA polymerase (RdRp) (2885 aa, 332.7 kDa). The M RNA encoded a non-structural (NSm) protein (309 aa, 34.4 kDa) and a viral glycoprotein precursor (Gn/Gc) (1122 aa, 127.4 kDa). The S RNA encoded a non-structural protein (NSs) (459 aa, 51.9 kDa) and the nucleocapsid (N) protein (278 aa, 30.6 kDa). This N protein shared amino acid identities of 80.9% with those of calla lily chlorotic spot virus. Our results suggest that the virus studied here belongs to a new tospovirus species, for which the name tomato zonate spot virus is proposed.