柑桔黄龙病毒研究初报

試驗用萊檬(Citrus aurantifolia)及麻疯柑(C.hystrix)作指示植物,用两广黃龙病区病株接穗嫁接接种,表現脉明、叶脉木栓化、茎部凹斑、及矮化、小叶等典型退化病毒(tristeza virus)所致症状,可知我国柑桔黄龙病与国外柑桔退化病(tristeza)系同一种病毒(或病毒群)所致。无病区的四川江津、湖南溆浦和北京的健康甜橙、桔类、及北京檸檬也带有黄龙病毒,可見黄龙病毒的分布远较病区为广。各种柑桔上所带黄龙病毒株系的強弱不同;在碰柑上的为强毒系,甜橙上的为强毒系或较弱毒系,桔类及北京檸檬上的各别为較弱毒系及弱毒系。

A PRELIMINARY STUDY OF THE CITRUS YELLOW SHOOT VIRUS

In experiments of grafting inoculation of the citrus yellow shoot virus, symptoms of vein cleaning, vein corking, stem pitting, stunting, small leaf and leaf yollowing on acid lime (Citrus aurantifolia) and Citrus hystrix seedlings are observed and found to be typical of tristeza. It is therefore tentatively concluded that the citrus yellow shoot virus might belong to the same entity as tristeza. In China the citrus yellow shoot disease is limited to the provinces of Kwangtung, Fukien, Taiwan and the Chuang Autonomous District of Kwangsi. The present study, however, reveals that this virus is also distributed in the non-epidemic areas: Szechuan, Hunan and Peking, where sweet oranges (C. sinensis, mandarins (C. reticulate) and Peking lemon (i. e., Meyer lemon) are symptomless carriers of the virus. According to the types of response of the two indicator plant species to inoculation, the isolates of citrus yellow shoot virus are tentatively grouped into three categories: severe, mild, and very mild. Results of our experiments show that the citrus Pokan carries only the severe isolates, varieties of the sweet orange carry both severe and mild isolates, while mandarins and Peking lemon carry mild and very mild ones respectively. Since Citrus hystrix was reported by Knorr in 1956 as an indicator plant for tristeza, it has been little used in certification and research work of tristeza. According to our experience C. hystrix as an indicator plant for tristeza is equally good as or even better than the Maxican lime.