Etiology And Pathogenic Mechanisms Of Medicinal Plants Atractylodes Chinensis Anthracnose

Atractylodes chinensis, a member of the Compositae family, is a perennial plant and widely distributed in Northwest, Northeast, North China, and so on. The dried rhizomes of A. chinensis and A. lancea have been used for centuries in Chinese traditional medicine, which is high valued as economic and medicinal. With the development and utilization of wild A. chinensis, the demand was increasing, resources were gradually reduced, and it became difficult to meet the market demand. To protect balance development of the wild resources and the natural ecological environment, the artificial cultivation of wild A. chinensis has been taken seriously. There was large scale artificial cultivation in Fushun, Benxi viz., Liaoning. The disease became more and more serious in the process of the wild resources domesticating, during which a new disease of A. chinensis was observed serious. There were still no reports on the disease. Thut, in order to provide theoretical basis for field identification and prevention on A. chinensis anthracnose, the occurrence and damage, pathogen identification, biological characteristic, the formation mechanism of appressorium and pathogenic mechanism of the disease were systematically studied.1. Surveying the disease of A. chinensis in Liaoning Province and classifying the status of the pathogen of A. chinensis anthracnose. This study researched the major species and dynamics occurrence of diseases on A. chinensis in seven major producing fields, such as Fushun, Qingyuan and Xinbin of Liaoning from 2011 to 2015. The results showed that there were three kinds of main disease, viz. leaf spot, anthracnose and sclerotinia rot. Of which, leaf spot and anthracnose of A. chinensis were more serious. The pathogen of leaf spot and sclerotia disease of A. chinensis was Paraphoma chrysanthemicola and Sclerotinia nivalis, respectively. The anthracnose disease of A. chinensis was first observed in Fushun, Liaoning. With the help of taxonomy expert, Dr. Ulrike Damm, and based on the morphology and cultural characteristics, and multi-locus molecular analysis, the causal agent was identified as a new spieces, and named as Colletotrichum atractylicola.2. Biological characteristics of C. atractylicola. Experimental results showed that the optimal temperature of the fungus hypha growth was 25℃, optimum temperature of spore production was 25 and 28℃. The conditions of little acid and alternation between light and dark were benefit. The optimum culture media were OA and RV8 on mycelial growth and spore production, respectively. The optimum carbon source was D-maltose. For conidia germinating, the optimum temperature is 25℃, germination rate was highest on concentration of 1×104/mL. Optimum relative humidity was 100%. No significant effect of light on the spore germination. Conidia could germinate during pH4-10, the most optimum pH was 7. Lethal temperature measurement results showed that the temperature for hypha and conidia was 57℃ and 59℃, respectively.3. Researching of the infection way and the formation conditions of appressorium of C. atractylicola. Appressorium play a leading role in the process of C. atractylicola invading the host. Occording to observe the infection of C. atractylicola on leaves, the fungus infected with appressorium formed after conidia germinating or hypha through the orifice or cuticle directly. Incubation period was about 2 to 4 d. The resauts of appressorium formation conditions showed that the optimum temperature was 28℃, and optimum humidity was 100%, which were consistent with the rules of disease occurrence and development. The rate of appressorium formatting was highest when the concentration was 1×104/mL. The appressorium formatted during pH5 to 10, with optimum pH of 7. There was no significant effect of light on appressorium formation.4. Definited the pathogenic mechanism of the disease. The cell wall degradation enzymes were one of the important virulence factors, played an important role in the process of spot expanding. The results of cell wall degradation enzymes activity on different times of A. chinensis anthracnose showed that pathogen produced six kinds of CWDEs, viz. PG, PMG, PEL, PNL, Cx and EG, but significant differences were in production conditions. The activities of CWDEs on diseased leaves were higher than that on uninoculated leaves, but they were significant different on different parts, in which disease spot produced the highest activities of CWDEs. Based on the testing of CWDEs activities in vitro, the results showed that the optimum temperature for producing CWDEs was 20℃ and 25℃. The condition of 12 h alternating oscillation was benefit to the production of CWDEs. Different conditions of culture time, pH of nutrient solution, light, carbon and nitrogen sources were influence significant to the 6 kinds of enzymes. The leaves inoculated with pectinase, pectin lyase and cellulose enzyme showed typical water spot, and the damaged abilities of pectinase and pectin lyase were stronger.