臺灣紅龍果病毒性病害之研究與現況分析

Abstract

紅龍果又名火龍果(pitaya, pitahaya, dragon fruit)，為仙人掌科(Cactaceae)三角柱屬(Hylocereus spp.)之多年生攀附性植物，原產於中南美洲熱帶雨林，為臺灣積極推廣且極具外銷潛力的熱帶果樹。目前紅龍果多以肉質狀三角莖扦插繁殖，雖可提供園藝性狀穩定、品質均一的種苗；但若繁殖用的母本遭受病毒感染，很容易經由種苗使病毒快速散播。臺大劉瑞芬教授的研究團隊於2001 年發表Potexvirus 屬之仙人掌X病毒(Cactus virus X, CVX)感染紅龍果植株引起斑駁病徵，他們完成CVX-Hu 分離株全長基因體之選殖與解序，並製備出CVX 抗血清，應用於DAS-ELISA 檢測。農試所廖吉彥等人的田間調查指出，CVX 普遍存在於臺灣與金門的紅龍果植株中，依地區不同感染率在50%~90%之間。我們實驗室於2005 年從臺大農場種植的紅龍果植株中分離出CVX-NTU 分離株，並完成全長基因體之選殖與解序工作。2006 年至2008 年間我們從陽明山採集的紅龍果樣品分離並鑑定出另外兩種Potexvirus 屬病毒：其一為臺灣首次發現之蟹爪蘭X 病毒(Zygocactus virus X, ZyVX)；其二為未被鑑定的新potexvirus，因而命名為紅龍果X 病毒(Pitaya virus X, PiVX)。目前臺灣所報導感染紅龍果的三種病毒皆為potexvirus，將CVX、ZyVX 與PiVX，以及其它Potexvirus 屬病毒進行序列比對及類緣分析，結果顯示感染仙人掌科植物的potexvirus 都屬同一個分群，代表彼此的類緣關係較密切。為了解這三種病毒在紅龍果的感染情況，我們研發出多引子反轉錄聚合酶鏈鎖反應(multiplex RT-PCR)，並進一步利用磁性奈米粒子，發展出magnetic nanoparticle-capture RT-PCR (MNC RT-PCR)快速檢測方法。我們對臺灣各地區種植的紅龍果進行田間調查，最新結果顯示所採集的田間樣品皆有病毒感染，相較於七年前的田間調查結果，三種potexviruses 感染情形明顯增加。 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.