Since 2002, papaya black rot has been spreading over several islands of Okinawa Prefecture, Japan. To devise a prevention strategy for the disease, microbiological research on the pathogen was conducted. Twelve strains were isolated from papaya infected with black rot showing symptoms such as water‐soaked lesions on stems and petioles, black spots on fruits, and rotted leaves turning yellow with necrotic spots. Through Koch's postulates, we confirmed that the isolated strains caused papaya black rot. Bacteriological assays showed that the strains have characteristics different from the type strains of Erwinia mallotivora, E. papayae, and E. psidii. Moreover, 16S rDNA sequence similarity searches showed that the isolated strains had less than 98.6% similarity with type strains. Additionally, phylogenetic analysis of 16S rDNA sequences suggested that the isolated strains were possibly a novel species belonging to the genus Erwinia, as the strains formed an independent cluster and had low sequence similarity with the type strains. Earlier studies indicated that papaya black rot is caused by E. cypripedii. Therefore, we propose to add the Erwinia sp. isolated in this study to the list of papaya black rot pathogens.

中文翻译：

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欧文氏菌属的特征。引起木瓜黑腐病（Carica papaya）首次在日本冲绳本岛记录

自2002年以来，木瓜黑腐病已蔓延到日本冲绳县的几个岛上。为了制定该疾病的预防策略，对病原体进行了微生物学研究。从感染了黑腐病的木瓜中分离出十二个菌株，表现出诸如茎和叶柄上浸水的病斑，果实上的黑斑以及腐烂的叶子变黄并带有坏死斑的症状。通过科赫的假设，我们证实了分离出的菌株引起了木瓜黑腐病。细菌学分析表明，该菌株的特性不同于Erwinia Mallotivora，E。papayae和E. psidii的类型菌株。。此外，16S rDNA序列相似性搜索显示分离出的菌株与类型菌株的相似性小于98.6％。此外，对16S rDNA序列的系统进化分析表明，分离的菌株可能是属于欧文氏菌属的一个新物种，因为该菌株形成了独立的簇，并且与该类型菌株的序列相似性较低。较早的研究表明，木瓜黑腐病是由E.cypripedii引起的。因此，我们建议添加Erwinia sp.。在这项研究中分离出的木瓜黑腐病病原体清单。