条斑紫菜(Pyropia yezoensis)绿斑病病原菌的分离鉴定

绿斑病(Green spot disease)是一种常见的海区栽培条斑紫菜(Pyropia yezoensis)病害，在整个紫菜栽培期间都可能发生，以每年11~12月份最为严重，主要出现在幼叶期和成叶期。首先，在叶状体上出现红色或淡红色小斑，而后逐渐转变为绿色，病斑继续扩展，在叶状体表面形成若干孔洞，后期几乎整个藻体变绿。本研究对日照地区患绿斑病的条斑紫菜进行病原菌分离纯化，得到5株优势菌(编号为Y1~Y5)，人工回感实验结果显示，Y1可以引起健康条斑紫菜发生绿斑病。对Y1进行了生理生化检测、16S rRNA、dnaA和dnaN基因序列分析，确定病原菌为海洋假交替单胞菌(Pseudoalteromonas marina)。对绿斑病的发病进程进行了观察，并检测了培养温度、海水比重和养殖密度等环境因子对绿斑病发生的影响，结果显示，高温和高密度养殖会加速绿斑病病情的发展，海水比重为1.022时，绿斑病发病较严重。本研究确定了一株引起条斑紫菜绿斑病的病原菌，并分析了部分理化因子对感染的影响，为条斑紫菜绿斑病的防控提供了基础数据。

Isolation and Identification the Pathogen of Pyropia yezoensis Green Spot Disease

Green spot disease is one of the major disease considerations in the farming of Pyropia yezoensis. Green spot disease could be found in all the periods of thallus, and outbreaks usually occur in November and December. At the start of infection, small light red spots could be found on the thallus, and then the spots gradually turned green and expanded quickly. Holes from lesions formed later in the surface of thallus. At last, the entire thallus became green and fell off. In this research, bacteria strains were isolated from P. yezoensis with green spot disease farmed in Rizhao. Experimental infection showed that the strain Y1 could cause P. yezoensis green spot disease. Biochemical characterization and genes analysis of 16S rRNA, dnaA and dnaN indicated that the pathogen Y1 was Pseudoalteromonas marina. Influence of environmental factors on the outbreak of disease were also characterized by experimental infection with different temperature, stocking density and gravity of sea water. The results showed that higher temperature and stocking density will accelerate the spread of the disease, but gravity of sea water within a certain range did not affect the occurrence of the disease. In this study, we described the green spot disease caused by P. marina, which provides information for disease control in P. yezoensis cultivation.