Study On Micro-Ecology Mechanism In American Gensing Continuous Croping Obstacles And Disease Resistance Of Bio-control Actinomyces

American Ginseng is one of the famous and presious medicinal plant, with extremely high medicinal and economic value, but the continuous cropping obstacles of panax quinquefolium is urgently to be solved by the "bottleneck" problems. This paper maily studies the ecology mechanism of the continuous cropping obstacles on Panax quinquefoium in Liuba county of shaanxi and the resistance function by bio-control actinomycetes. The results are as follows.1. The research on the soil microbial ecology between the rhizophere and root surface of the diseased and healthy American Ginseng shows that:①The number of bacteria and actinomyces in the rizosphere of diseased plant decreased by 63.9% and 33.5%, while fungi increased by 160.1%, compared with healthy plant. The B/F and A/F value in the rizosphere soil of diseased plant decreased by 86.1%,74.3%, respectively ,comparing to the healthy. The number of bacteria, fungi in the root surface soil of diseased plant increased by 31.4% and 29.8%, while actinomycetes decreased 79%.②The quantity of soil available nutrition (N, P, N) and organic matter in the rizophere soil of disesaed plant increased by 2.8%, 35.4%, 69.7% and 10.2%, respectively, compared with the healthy.2. The study on the microbial ecology between the roots of the diseased and healthy American Ginseng and the separation of pathogenic fungi from the diseased root shows that:①The quantity of bacteria and fungi in the root of diseased plant increased 3182.3% and 40.6%, comparing to the healthy one; Actinomyces was not isolated from the diseased and healthy plant.②The percentage of Plectosphaerella cucumerina in the total root fungi is 80%. Fusarium solani was only isolated from the healthy American Ginseng.3. There were 6 kinds of predominant fungi in the rhizosphere soil and root surface between the diseased and healthy American Ginseng. 4 kinds of fungi, identified by the ITS sequence analysis methods, were Plectosphaerella cucumerina, Fusarium solani, Fusarium oxysporum, Penicillium funiculosum. The proportion of Plectosphaerella cucumerina both in the soil surface of diseased and healthy plant were 84.3%, 46.1%, respectively. Similarly, Fusarium solani were 13.7%, 35.3%. Plectosphaerella cucumerina , the quantities of which in the root surface of diseased plant increased 2523.8%, comparing to the healthy plant, was closely related with the illness of American Ginseng, probably.4. The research on inhibition and mechanism of bio-control actinomycetes against pathogen shows that:①10 strains of antigonistic actinomyces had inhibitory effects on the growth of fungal pathogen of American Ginseng and Ginseng. The diameters of inhibitory zones of Act24-1 and Act24-2 against Neonectria radicicola were 22.5, 21.5mm, respectively; The diameters of inhibitory zones of Act24-2, Act7,D141 and Act1 against Phytophthora cactorum were distributed between 21.5 and 24.0mm.②The axenic fermentation extracts of 8 strains of actinomyces can inhibit the growth of fungal pathogen. The inhibitory rates of Axenic fermentation extracts of Act24-2 to the Phytophthora cactorum, Cylindrocarpon sp. and Neonectria radicicola were 83.3%, 76.4% and 64.4%, respectively. 5 strains of fungal pathogen of Ginseng and American Ginseng could induce selected actinomyces to produce chitinases and cellulase. Selected actinomyces, contacting with the mycelia of pathogen, can dissolve the hyphae of pathogen and inhibit the infection of pathogen by producing cell wall degrading enzyme, such as chitinases and cellulase. This reveals the mechanism of bio-control actinomycetes against specific pathogen fungi from the angle of zymolysing.5. The research on isolation, identification of the fungal pathogen from diseased root of American Ginseng in Liuba and infection of American Ginseng and Ginseng by suspected pathogens shows that:①9 strains of suspected pathogen repersented different degree of infection to the root of American Ginseng and Ginseng. Fusarium solani has strong infection to both American Ginseng and Ginseng; The root of American Ginseng and Ginseng showed different degree of symptoms after infected by the same suspected pathogen, such as Fusarium oxysporum can infected Ginseng root seriously, but had weak infection to American Ginseng root, however, Fusarium solani play the oppsite role.②The disease of American Ginseng in Liuba county was caused by Fusarium solani and Fusarium oxysporum, probably.6. Serious diseases occurred to American Ginseng after 6-years crop rotation of the soil, the mortality of American Ginseng seedling was over 95%. The study on soil microbial ecology between rhizosphere and root surface of healthy American Ginseng and root surface of diseased one shows that:①For the healthy plant, the number of fungi and actinomyces in the rhizospere soil of the inferiror increased 39.9%, 24.8%,respectively, while the bacteria decreased 16.1%. The amount of bacteria, fungi and actinomyces in the root surface soil of inferior plant increased 4735.5%, 74.4% and 64.4%, respectively, comparing to the superior plant.②For the diseased plant, the amount of fungi and bacteria in root surface soil of heavy infected plant increased 9970.3%, 297.5%, comparing to the light infedcted one.③the quantity of soil nutrition of the inferior plant were lower than the superior one, of which, the amount of available N and organic matter decreased 49.9%, 55.1%, respectively, compared with the superior plant.