並列摘要
The achievements of citrus virus studies of the world in the past decade or two have directed our attention to the importance in this field. Besides the known 'Likubing' in Taiwan, the author has, recently, proven the existence of at least three other citrus virus diseases in Taiwan, namely exocortis, psorosis and cachexia-xyloporosis. Owing to the resistence of Rangpur lime and trifoliate orange to tristeza to which 'Likubing' belong, these rootstocks have been used in Taiwan to some extent without knowing that these happen to be intolerent stocks to exocortis. Thus recommendation of using these stocks cannot be wisely made unless proper precautions are taken. Further, the transmissibility of exocortis through tools and fingers makes the existence of this disease more important. Up to the present, recognized citrus virus diseases are so numerous and indexing of all of them so tidious that the utilization of nucellar citrus lines, though require considerable time to develop, has ultimately become very practical. Sooner or later it will become an appropriate trend for us to follow if goal of citrus improvement is to be attended.