Journal of Taiwan Agricultural Research

Author:Ting-Chin Deng*, Yi-Ting Lin, Chin-Hui Tsai, Jye-Yann Liao, and Ruei-Lung Kao

Abstract:

      Leaf samples with mosaic and malformation on Dioscorea alata and that with yellowing and mosaic symptoms on Diosocoreab atatas were collected for inoculation tests. Both of them developed local lesions on Chenopodium quinoa, and two virus isolates ‘YA3’ and ‘Yam-7’ were obtained through single lesion isolation. YA3 and Yam-7 both with spherical visions were observed by electron microscope and they reacted with antibody to Broad bean wilt virus 2 (BBWV-2) were detected by ELISA. When back-inoculated to Dioscorea spp., tested plants of some cultigens with latent infections showed symptoms only in the following years and the virus was detected by ELISA. With Fabavirus common primers Fab5’R1F/Fab5’R1R, reverse transcription-polymerase chain reaction (RTPCR) was conducted to amplify a 390 bp DNA product from both of YA3 and Yam-7. The nucleotide sequence of this fragment sharing 94.1% identities between YA3 and Yam-7. Comparing with other isolates, YA3 shared 93.1% identities with Bupleurum chinense isolate of BBWV-2. Moreover, with BBWV-2 specific primers BBWVSSP/BBWVKMRM to conduct RT-PCR, both YA3 and Yam-7 obtained a 320 bp product. The identities between YA3 and Yam-7 of this nucleotide sequence fragment were only 88.1%. Comparing with other isolates, YA3 was 86.3% identical to the Japanese isolate of BBWV-2 infecting yams. However, this Japanese isolate shared 96.5% identities with yam-7. Results of phylogenetic analysis also show that YA3 and Yam-7 are closely related and belonged to a BBWV-2, which is different from other species of fabaviruses. This is the first report of BBWV-2 infecting yams in Taiwan.

Key words:Fabavirus, Primer, RT-PCR, Nucleotide sequence, Phylogenetic analysis

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