臺灣發生之喜姆比蘭嵌紋毒素病

Virus Disease of Orchids Caused by Cymbidium Mosaic Virus in Taiwan

由本省中部地區採集之蘭花包括嘉德麗亞、石斛、文心、喜姆比、萬代和蝴蝶蘭，經電子顯微鏡檢查，生物檢定及毒素物理性質之測定，證實感染喜姆比嵌紋毒素病（Cymbidium mosaic virus）病株之共同特微為老葉片出現暗褐色略為陷之嵌紋，其大小形狀依蘭花種類而異，病株所開之花一般沒有病微，病毒很容易經由法液藉磨擦或刀剪造成之傷口傳染至健株。病毒在Cassia occidentalis上磨擦接種，2~3天後即可產生局部性病斑，利用此法行生物檢定可於短期內鑒定病株。供試毒素在汁液內之不活化溫度為56和58℃之間，稀釋終點在10^(-5) 和10^(-6) 之間，在20℃定溫箱內可耐保存達19天之久，但如用Millipore除去其他微生物則耐保存可延到40天以上，毒素顆粒在電子顯微鏡下為長條形略為彎曲，其大小為18×490nm。

A virus disease caused by Cymbidium mosaic virus was identified from diseased orchids of Cattleya, Cymbidium, Dendrobium, Vanda, Oncidium and Phalaenopsis collected from southern and central part of Taiwan, based on electron microscopical examinations, bioassay and physical properties of the virus. The disease was characterized by sunken dark brown spots or streak of various forms and sizes on older leaves. The flowers were usually symptom-less, The, virus was easily transmitted through mechanical means of alternate outtings of diseased plants and healthy plants, and of rubbed with expressed juice from diseased plants. Local lesions were formed on Cassia occidentalis 2~3 days after inoculation, which provided a rapid method of bioassay for identification of the virus. The thermal inactivation point of the virus was between 56 and 58℃, and the dilution end-point was between 10^(-5) and 10^(-6). Aging in vitro was 19 days at 20℃ and was more than 40 days when juice of infected plant was filtrated through 0.45μ Millipore kept at the same temperature. Under electron microscopy, the virus particles were sinuous rods with the size of 18×490 nm.