柚类果树叶片斑驳病的病原鉴定与检测

Identification and detection of pathogen causing mottle leaf of pomelo

柚类是柑桔中的一类重要品种，在我国有广泛的分布。近年来，在福建等产区发现柚类病树日趋增多，其病状为叶片斑驳、小果、植株矮化，暂称为叶片斑驳病。本病能通过组织嫁接从病柚树传染到柚健苗和芦柑健苗。在电镜下观察，其病原菌体的形态和细胞壁构造与柑桔黄龙病的病原（Ｌｉｂｅｒｏｂａｃｔｅｒａｓｉａｔｉｃｕｍ）十分相似。应用柑桔黄龙病病原ＤＮＡ的特异性引物进行ＰＣＲ试验产生的ＰＣＲ产物，其分子量与柑桔黄龙病病原ＤＮＡＰＣＲ产物的基本相同，为５６３ｂｐ．；以及应用柑桔黄龙病病原的特异性探针与其ＰＣＲ产物进行Ｓｏｕｔｈｅｒｎ杂交试验，能产生杂交反应；这些都表明在柚树病原ＤＮＡ与柑桔黄龙病病原ＤＮＡ之间存在着十分高度的同源性。综上结果证明：柚类叶片斑驳的病原很可能与柑桔黄龙病病原是相同的，或其关系是十分密切的。

Pomelo is a group of popular cultivars of citrus in China. In recent years, diseased plants of pomelo have been found in Fujian production areas. The symptoms of the diseased trees include leaf mottle, small fruit and stunting. The disease is graft\|transmissible from diseased plant to healthy pomelo and ponkan via tissue grafting. The morphological characteristics of the pathogen resemble those of Liberobacter asiaticum which causes citrus Huanglongbing (formerly citrus greening) based on electron microscopy. The PCR products of pathogen DNA obtained with gene\|specific primers for Huanglongbing liberobacter and Southern hybridization of the PCR products with oligonucleotide probe specific for the liberobacter pathogen show that there is a remarkable degree of DNA homogeneity between the pathogen from diseased pomelo and that of citrus Huanglongbing plants. Taken together, the results of this study show that the causative agent of pomelo disease is either identical or very closely related to the asiaticum which causes citrus Huanglongbing.