一起条斑紫菜拟油壶菌病的诊断

Diagnosis of Oplidiopsis disease in Pyropia yezoensis

中文关键词: 条斑紫菜  拟油壶菌病  cox1  紫菜拟油壶菌

英文关键词: Pyropia yezoensis  Oplidiopsis disease  cox1  Oplidiopsis sp.

中文摘要:

      赤腐病(red rot disease)和拟油壶菌病(Oplidiopsis disease)是海上栽培紫菜(Pyropia)的主要病害，常引起紫菜大面积病烂。2019年1月江苏省盐城市大丰区某条斑紫菜(Pyropia yezoensis)栽培海区有134 hm2发生了紫菜病烂，本研究对该起病烂进行了病害调查和病原鉴定。结果显示，患病紫菜的病症与拟油壶菌病一致，主要表现为发病初期，在叶片边缘、基部和中部出现粉红色的病斑，随着病程发展，病斑逐渐褪色并扩大；发病后期，整个叶片颜色变浅，叶片组织溃烂脱落；在显微镜下可观察到紫菜细胞内寄生1~4个圆球状菌体，菌体内有多个油滴状物质。以病烂紫菜叶片或其匀浆液为感染源，分别在10℃和20℃条件下进行人工感染实验，二者均能使正常紫菜出现拟油壶菌病的病症。对现场采集及人工侵染后的病烂紫菜疑似病原进行cox1基因测序和系统发育学分析。研究表明，所测cox1基因均与紫菜拟油壶菌(Oplidiopsis porphyrae、O. pyropiae、O. porphyrae var. koreana)聚为一支，相似度为100%。综上所述，该起条斑紫菜的病烂由紫菜拟油壶菌(Oplidiopsis sp.)引起。

英文摘要:

      Red rot and Oplidiopsis disease are the main diseases that occur during the farming of Pyropia (Bangiales, Rhodophyta) cultivated in the sea, which cause large areas of Pyropia to rot. Oplidiopsis disease is caused by Oplidiopsis sp., which is a biotrophic parasitic oomycete and there is currently no in vitro culture method for this species. The pathogen can only be identified by high-resolution microscopic observation and molecular methods. Experimental infection is typically undertaken by culturing diseased Pyropia with normal blades. In January 2019, 2000 acres of Pyropia disease occurred in a P. yezoensis cultivation area in Dafeng District, Yancheng City, Jiangsu Province, causing a large decrease of the P. yezoensis yield. We performed an investigation and pathogen identification of this disease. By macroscopic observation and studying the histopathology characteristics of the diseased thalli using a microscope, the Pyropia symptoms were found to be the same as that of the Oplidiopsis disease. The main symptoms were as follows: Pink spots appeared at the edge, base, and middle of the thallus at the beginning of the infection, which gradually faded and expanded as the disease progressed. During the late infection stage, the entire thallus became lighter and the tissue broke down and fell off. One to four spheroid parasitic oomycetes were found in one Pyropia cell, which contained multiple oil drop-like substances. Diseased thalli or their homogenates were used for experimental infection, with all causing Oplidiopsis disease symptoms in normal thalli at 10℃ and 20℃. To identify the pathogen, cox1 gene sequencing and phylogenetic analysis of the naturally and experimentally infected thalli were performed. The results showed that the pathogen sequences were clustered with O. porphyrae, O. pyropiae and O. porphyrae var. koreana with 100% similarity. In summary, the disease of P. yezoensis in Dafeng District was found to be caused by Oplidiopsis sp.