应用FBA染色法观察柑桔黄龙病病株中的病原难培养细菌

病株新梢主叶脉或嫩茎横切片用 FBA 染色工作液染色5～8min,在光学显微镜(油镜)下可见到其外向韧皮部筛管细胞中存在被染成红褐色的病原难培养细菌,菌体大小为0.35～0.65μm × 1.70～4.00μm,多为杆状,有些呈长亚铃形或长椭圆形。而健株、衰退病株、裂皮病株、溃疡病株,生理黄化株和田间天牛为害黄化株等的叶脉或嫩茎韧皮部筛管细胞中均未见到任何菌体存在。FBA 染色法快速、简便、准确,可作为诊断柑桔黄龙病的一种实用方法。本文还就超薄切片电镜观察黄龙病病原检出率低的原因进行了探讨。

THE DETECTION OF THE GERMS ASSOCIATED WITH CITRUS YELLOW SHOOT DISEASE IN DISEASED TREES BY FBA STAINING METHOD

FBA Staining Method,a new histochemical method was used to detect the germs (fastidious bacteria or bacteria-like organism)associated with citrus yellow shoot(CYS)dis- ease in diseased citrus trees.The result shows it is a rapid,simple and useful method for di- agnosing CYS-infected trees.The hand sections of leaf veins or stems were prepared from fresh tissues of CYS-infected and healthy citrus plants,and then treated with FBA Staining Method.A large number of germs in red-brown color were observed in the extroverssion phloem cells(sieve tube cells)of the leaf veins and stems of the citrus trees with CYS disease, but none in the healthy plants,and none in those with tristeza,execortis,canker,physio- logical yellow or be harmed by lengicorn,too,under a light microscope(1000-2000x).Most of the germs were rod-shaped,and some were longish dumbell-shaped or longish ellipse-shaped with the size of 0.35—0.65μm×1.70—4.00μm.The reason that a low rate of the germsassociated with CYS disease could be detected by electron microscopes was also dis- cussed.