Author：Chang, Y.-C.^1,*, Kuo, T.-Y.², Mao, C.-H.¹, Lu, Y.-C.¹ and Li, Y.-S.¹

Abstrct：

    Pitaya, also called pitaya, pitahaya or dragon fruit, belonging to the genus Hylocereus in the family of Cactaceae, is a perennial climbing epiphytic plant native to the forests of Latin America, and is becoming an important tropical fruit crop in Taiwan. Because pitaya is mainly propagated by cutting, if mother plant is infected with viruses, disease can be spread easily. In 2001, the research team of Professor Ruey-Fen Liou at National Taiwan University published the first report of Cactus virus X (CVX), a member of the genus Potexvirus, on pitaya in Taiwan. They finished the cloning and sequencing work of CVX-Hu isolate, prepared the antiserum and developed the DAS-ELISA. The result of disease survey done by Liao et al. at Taiwan Agriculture Research Institute indicated that CVX was widespread in the pitaya plants and the infection incidence ranged 50%~90% in different areas of Taiwan and Kinman. In 2005, we isolated a new strain of CVX from the pitaya grown in the experimental farm at National Taiwan University, and obtained the complete genomic sequence of CVX-NTU. Another two potexviruses were isolated and identified by our laboratory in the pitaya samples collected from the Yanmingshan orchard during 2006 to 2008. One of the potexvirus is Zygocactus virus X (ZyVX) which was first identified and reported on pitaya in Taiwan. The other one is Pitaya virus X (PiVX) which is a new species of potexvirus first found in pitaya. The results of phylogenetic analyses on the full-length genomes of CVX, ZyVX, PiVX and other published potexviruses demonstrated that all Cactaceae-infecting potexviruses belong to the same cluster. For field survey of CVX, ZyVX and PiVX in pitaya plants, we developed a multiplex RT-PCR method, and later a magnetic nanoparticle-capture RT-PCR (MNC RT-PCR) was also developed. Pitaya plants sampled from several production areas in Taiwan were investigated for the infection rate and distribution of potexviruses. The recent field survey of pitaya showed that all pitaya samples were infected by potexviruses and the infection rate of these three potexviruses increased significantly compared to seven years ago.

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¹ Department of Plant Pathology and Microbiology, National Taiwan University
² Master Program for Plant Medicine, National Taiwan University
* Corresponding Author; E-mail：ycchang@ntu.edu.tw

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