Purpose To investigate the occurrence of viral disease on Phalaenopsis aphrodite sold in the market in Kunming, Yunnan Province.
Methods RT-PCR detection was conducted in 17 P. aphrodite samples collected from the market with virus-specific primers including cymbidium mosaic virus (CymMV), odontoglossum ringspot virus (ORSV), tomato mottle mosaic virus (ToMMV), and so on. The amplified fragments of related viral genes were cloned, sequenced and comparative analyzed.
Results Four viruses were detected in seven P. aphrodite samples: ORSV, CymMV, tomato spotted wilt orthotospovirus (TSWV) and ToMMV, with detection rates of 35.29%, 23.53%, 5.88% and 5.88%, respectively. Among them, ORSV and CymMV were the two dominant viruses of P. aphrodite in Kunming market, and the co-infection rate of them was 23.53%. Meanwhile, ToMMV was detected in P. aphrodite for the first time. No cucumber mosaic virus (CMV), impatiens necrotic spot orthotospovirus (INSV) and tomato zonate spot orthotospovirus (TZSV) was detected. P. aphrodite is a new natural host for ToMMV, and the ToMMV inoculated P. aphrodite plants showed no obvious symptoms. Nucleotide sequence identity of the complete cp gene sequence of ToMMV P. aphrodite isolate (YKMHDL, GenBank Acc. No.: PP445225) was analyzed with those of 19 ToMMV isolates worldwide. The cp gene nucleotide sequence identity of these 20 ToMMV isolates was from 98.12% to 99.79%. Phylogenetic tree based on the cp gene of different ToMMV isolates revealed that the ToMMV-YKMHDL isolate was closely related to the ToMMV Yunnan pepper isolate and Yunnan pea isolate, but it was more distantly related to the isolates outside China.
Conclusion ORSV and CymMV are the two dominant viruses found in P. aphrodite sold in Kunming. This is the first report of natural infection of ToMMV in P. aphrodite as well as plants in family Orchidaceae. The asymptomatic presence of ToMMV in P. aphrodite has the potential to lead to extensive and long-distance transmission of the virus.
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