Isolation, Identification And Pathogenicity Research Of The Pathogen Of Slippery Scar Disease In Auricularia Polytricha

Auricularia polytricha is an important cultivated mushroom, which is cultivated abroadly with bags in Fujian, Sichuan, Henan, Hubei and Jiangsu province. In2009, a new disease which was called the slippery scar disease in Auricularia polytricha was found. It caused serious economic losses.We surveyed the occurrence rules, isolated and identified the pathogeny, texted the pathogenicity according to the Koch’s Postulation and studied the pathogenic factors in this work.One fungus was isolated from the infected mycelia by conventional tissue isolation, which was identified as Scytalidium lignicola by morphologic and microscopic observating and rDNA sequence analysising. There is no record ever before about diseases caused by this pathogeny on mushroom.Two programs were used in the pathogenicity test. One involved the simultaneous inoculation of the mycelia of A. polytricha and S. lignicola into both ends of cultivated bags. The other involved the inoculation of S.lignicola into the cultivated bags with full A. polytricha mycelia. The symptoms appeared in both of them was the same with the field symptoms. Re-isolated the diseased parts, the re-isolation was the same as the S.lignicola on the cultural traits and ITS sequence. The fungus isolated was the pathogeny of the disease.Three pathogenic factors were researched in this work, including the extracellular enzymes, toxin and the melanin.The pectinase, cellulose and proteinase could be detectived in the filtrate of S.lignicola which was cultured in PD shake flask. The pectinase included PG, PMG, PGTE, PMTE and PME. PME had the highest activity, which could be44.61U/mg, it meaned the S.lignicola hyphae’s activity of removing methyl from pectic substance and producing pectic acid was so high. The PG and PMG activity was lower, which meaned the S.lignicola hyphae’s activity of hydrolyzing pectic substance was low. PGTE and PMTE activity was instability, which meaned the S.lignicola hyphae’s activity of hydrolyzing pectin and pectic acid was unstabitily. The Cx kept high activity from the fourth day, which meaned the endo-glucanase activity of S.lignicola hyphae was high. Pro activity kept high activity in the later stage of culturing. The toxin was extracted by three ways, and the quality of which was tested by dialysising and autoclaving. The toxin filtrate and dialisised filtrate both had the pathogenicity to A. polytricha, while autoclaved filtrate had no influence on it.SDS-PAGE analysis showed no band, the toxin was conjectured as polysaccharide.The melanin extraceted by acid precipitation was rich. The results of the analysis on the dissolubility, stability and inoxidizability showed that the melanin could dissolve in alkali, be insoluble in acid and organic reagent. It was stability but the inoxidizability was low. From the UV spectrum, IR spectrum, NMR and tricyclazole restraining results, the melanin was conjectured as DHN.This three factor effected each other and destroyed the A. polytricha’s physiological function by affecting the cells’ultrastructure. The detail of the pathogenic mechanism was unknow, more work needed to be done.