Study On The Red Rot Disease And Olpidiops Disease Of Porphyra Haitanensis

Different samples of Porphyra haitanensiswere collected from Fuding, Xiapu,Jinjiang (Fujian Province) and Cangnan area (Zhejiang Province) respectively since2009to2012. The results of observation of rot on Porphyra haitanensis leaves indicatedthat the simultaneous infection by two diseases, red rot disease and olpidiops diseases,caused by Pythium porphyrae and Olpdiopsis sp. respectively, were confirmed to be themajor causes of the rotten laver diseases. The mycelia of Pythium porphyrae penetratedinto the cells. The infected cells started to atrophy and dying gradually in a few days,meanwhile the color turned from red to green. Then the cells became rotten and broken,leaving holes in the thalli. In asexual life cycle, biflagellate, kidney-shaped zoosporeswere released from the sporangium. In sexual life cycle, antheridia and oogonia couldform under a particular condition. Olpdiopsis sp. invaded the cells, formed sporangium,then broke the cells at last. The sporangium released zoospores to infect more laver.Increasing drying time, decreasing density of cultivation, cultivation far away bayou, aswell as cold preservation can reduce the loss caused by diseases in a certain degree.The mycelia strain FM1was isolated from diseased thalli and maintained oncorn-meal seawater agar(CMSA). The artificial infection experiment displayed that theexperimental thalli was rotten like the thalli collected from the sea field. That meansstrain FM1was pathogen. According to analysis of the ITS rDNA(contained5.8S),strain FM1was high similar to Pythium porphyrae. Combining morphological withmolecular methods, this study revealed that Pythium porphyrae was the pathogen whichcaused the rot of Porphyra haitanensis.The disease is called red rot disease.The morphology of Pythium porphyrae,included mycelia, oogonia, antheridia, was observed on the corn-meal seawater agar(CMSA). Development of oogonia, cleavage of(cell division without cell growth) oosperm and the attachment and development ofswarm spore was also observed by optical microscope. The mycelia of Pythiumporphyrae could get a rapid growth in a favorable temperature from10to30℃and itsoptimum growth temperature is20℃.It could enjoy a rapid growth in a salinity rangefrom8to20, the optimum growth salinity is14.