Isolation And Identiifcation Of Fungal Pathogens In Atractvlodes Macrocephala And Selection Of Plant Growth-promoting Rhizobacteira (PGPR)

Atractylodes macrocephala Koidz. belongs to Compositae genus Atractylodes family,with the characteristis of warm in nature, sweet and bitter in taste. A. macrocephala is a verycommonly used herb in Chinese herbalism to build "Qi"(energy), strengthen digestion,eliminate dampness, and boost the immune system. It mainly distributes Zhejiang, Anhui,Jiangxi, Hunan, Sichuang and Hubei province etc. Continuous cropping of A. macrocephalashow the disadvantage of it growth and production, so the land should fallowed more than5years after A. macrocephala harvest. However, with the demand for A. macrocephalaincreasing，the current situation of A. macrocephala continuous cropping is becoming moreand more popularity. The plants of A. macrocephala were easier to be infected by diseases withcontinuous cropping system, leading to the lost in production and decreased the quanlity. Inorder to reduce the loss, local farmers usually chose pesticide and chemical fertilizer to solvethe diseases and growth problem, which have a strong negative impact on the quality ofmedicinal materials and its geoherbalism.This article studied the continuous cropping A. macrocephala from yuan-tang forest farmin Panan country, Zhejiang province. We surveyed the disease incidence of A. macrocephala,and isolated and identified the pathogen fungus that causing disease, also, we screened plantgrowth promoting rhizosphere bacteria (PGPR) from A. macrocephala, hoping to selectsuitable PGPR strains. The main results are as follows:(1) Investigation of the fungal diseases on A. macrocephalaBy means of field investigation and sampling, we confirmed root-stem rot and leaf spotdisease on A. macrocephala. Root-stem rot is one of the most common disease for continuouscropping A. macrocephala, diseased plants’ root and stem turn rot gradually, until the wholeplant die; During the early period of leaf spot disease, leaves grow rounded or inregular spot, then the spot gradually extend to the whole plant’s leaves, which affected the normalphotosynthesis of plants, and led to the deaths.(2) Isolation and identification of A. macrocephala fungal pathogensAccroding to morphological observation and molecular identification, we confirmedpathogenic bacteria of A. macrocephala root-stem rot are Fusarium oxysporum and F.incarnatum. Pathogenic bacteria of leaf spot is Alternaria longipes, which is first found on A.macrocephala(3) Isolation and screening the PGPR of A. macrocephalaWe obtained21bacteria strains from the root of A. macrocephala, number B1-B21. Thenwe accord to external antagonis ability, phosphate solubling ability and IAA produing abilityto screen PGPR strains. On the basis of antagonis ability,we selected11strains bacteriastrains, they are B1、B2、B4、B5、B8、B10、B11、B12、B17、B19and B21, B11’s antagonisrate of two kinds of pathogenic fungus is the most significant. The hightest rate is70.27%(antagonism to F. incarnatum). According to whether have the abbility of phosphate solubling,we selected8strains, they are B2、B10、B11、B12、B14、B15、B17and B21, among thesebacteria, B15has the best phosphate solubling ability, the ratio of yellow transparent circlediameter and colony diameter is2.27. Based on whether have the ability of producing IAA,we selected15strains, they are B1、B5、B6、B7、B9、B10、B12、B13、B14、B15、B16、B18、B19、B20and B21, among thesestrains, strain B5produces55.951mg/L IAA.(4)Molecular identification of of A. macrocephala’s PGPR16S rDNA result showed that: B1as Pantoea spp.; B2、B10、B12、B19、B21are identifiedas Bacillus spp., among which B10as Bacillus subtilis and B12as Bacillus megaterium; B3、B4、B5、B6、B7、B9、B13、B14、B15、B16、B18and B20are identified as Enterobacterspp.; B8as Pseudomonas chlororaphis; B11as Pseudomonas putida.