Etiological Study Of The Red Rot Disease On Pyropia Yezoensis

Pyropia yezoensis is a kind of important seaweed farming breed in China. Thedisease has become one of the reasons hindering seaweed farming and some studieson the pathogen and pathogenic mechanism of Pyropia yezoensis at home and abroad.In this study, the red rot disease of etiology study, aiming to provide theoretical basisfor the disease control and resistance breeding of Porphyra yezoensis.The mainresearch contents are as follows:1. Studies on the pathogenicity of Pythrium porphyrae of Porphyra yezoensis.Red rot is a kind of disease, caused by Pythrium porphyrae, which is fungal pathogen.In this study, the Pythrium porphyra NBRC33253which bought from BiologicalResource Center of Japan was analyzed by morphology and ITS sequence, and resultsshowed that the strain was the Pythrium porphyrae indeed. Then the study on growthcharacteristics of Pythrium porphyrae, found it had the fastest growth at temperatureof28℃, salinity of20psu. Artificial infection experiment and histopathologicalobservation found that the strain can cause treak laver typical red rot symptoms ofPorphyra yezoensis.Single factor on artificial infection experiment showed that hightemperature and low salinity may accelerate the disease, hyphae concentration had nosignificant effect in the range of0.001g/100ml-0.1g/100ml. Using the orthogonaldesign analyzed of infection of Pythrium porphyra and disease development fromtemperature, seawater salinity and hyphae concentration.The results showed that thetemperature on the occurrence and development of red rot disease had extremelysignificant influence;the seawater salinity on the occurrence and development of redrot disease had significant effect. Temperature23℃, salinity24psu, infected hyphaeconcentration0.001g/100ml-0.1g/100ml, red rot disease is the fastest, the mostserious illness.2. The red rot disease of Porphyra yezoensis caused by Alternaria.The Porphyrayezoensis farming of JiangSu occured massive red rot disease in mid November2011.We identified a strain of Alternaria isolated from sick Porphyra yezoensis and artificial infection experiment found that thestrain caused disease symptoms is similarwith the red rot symptoms caused by Pythrium porphyrae.The identification ofmorphology and the6conserved genes in developmental biology, the strain wasidentified as Alternaria porphyrae.The study on growth characteristics of Alternariaporphyrae, found it had the fastest growth at temperature of24℃, salinity of20psu.Using the orthogonal design analyzed of infection of Pythrium porphyra and diseasedevelopment from temperature, seawater salinity and spore concentration.The resultsshowed that temperature and seawater salinity on the occurrence and development ofred rot disease had extremely significant influence. Temperature23℃,salinity24psu,infected spore concentration102/ml-105/ml, red rot disease is the fastest, the mostserious illness.