Isolation and Identification the Pathogen of Pyropia yezoensis Green Spot Disease

Abstract:

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.