A strain of pathogenic bacterium was isolated from the blades of wild type Porphyra haitanensis with red-rotting disease collected from the wild population along the coasts of Pingtan Island of Fujian Province.The bacterium had a 100% similarity with Cobetia marina(Oceanospirillales,Proteobacteria) according to analysis of the 16S rDNA array.After the pathogenic bacterium was cultured in liquid medium for a period of time,an amount of bacterial suspension was inoculated onto the blades of different Porphyra...