Study On The Action Characteristics Of Four Allelopathic Autotoxic Substances On Soil Microorganisms And Main Pathogenic Bacteria Of Panax Notoginsen

Panax notoginseng[（Burk.）F.H.Chen],a traditional Chinese herbal medicine,is a perennial plant of the Araliaceae ginseng species.It is mainly produced in Wenshan Prefecture,Yunnan Province.It has a long history of planting and is one of the most distinctive biological resources in Yunnan Province.Due to the serious continuous cropping obstacle of P.notoginseng,the autotoxicity effect is one of the important factors causing the continuous cropping obstacle of P.notoginseng.Phenolic acids and saponins are the main autotoxins of P.notoginseng.In this study,the characteristics of soil microorganisms affected by four kinds of allelopathic autotoxins were studied in order to clarify the interaction between four kinds of allelopathic autotoxins and microorganisms in the rhizosphere or bulk soil of P.notoginseng,and to provide a favorable basis for alleviating the allelopathic autotoxicity of P.notoginseng and solving the problem of continuous cropping obstacles.In this paper,two-year-old P.notoginseng was used as the research object,and the Illumina Mi Seq platform was used to sequence and compare the microorganisms in rhizosphere and bulk soil with exogenous four kinds of allelochemicals to explore the interaction of allelochemicals with microorganisms in soil.The results are as follows 1.Principal co-ordinate analysis showed that exogenous vanillic acid significantly changed the fungal and bacterial community structure in the rhizosphere soil of P.notoginseng,while the difference of p-hydroxybenzoic acid was not obvious.The relative abundance of Pseudomonas,Enterobacter,Pseudogulbenkiania and Sphingobium increased significantly after exogenous vanillic acid,while the abundance of RB41,Bryobacter and Haliangium decreased significantly.The abundance of Volutella and Spizellomyces increased significantly,and the abundance of Humicola decreased significantly.The abundance of Solicoccozyma,Saitozymazai and RB41 increased significantly in the treatment group at VA2 concentration,and the abundance of Streptomyces decreased significantly.2.Exogenous vanillic acid significantly increased the relative abundance of potential pathogenic,while p-hydroxybenzoic acid significantly inhibited the overall abundance of potential pathogenic;log₂-fold change analysis showed that both phenolic acids up-regulated the abundance of Fusarium.3.The response of microbial diversity index in bulk and rhizosphere soil after exogenous notoginsenoside R₁and total saponin was different:under the condition of high concentration R₁（30μg/g）and total saponins（90μg/g）,the bacterial OTUs,Chao1 and Shannon diversity index and fungal OTUs and Chao1diversity index in bulk soil decreased significantly.Only Shannon diversity index of rhizosphere soil bacteria decreased significantly.4.Principal co-ordinate analysis showed that R₁and total saponin significantly changed theβdiversity of fungal and bacterial communities in the bulk soil,but only significantly changed theβdiversity of fungal communities in the rhizosphere soil.5.Exogenous notoginsenoside R₁and total saponin could significantly increase the abundance of bacteria Sphingobium and Novosphingobium in bulk soil,and high concentration of total saponin（90μg/g）could significantly increase the abundance of Fusarium,Cylindrocarpon and Tetracladium.Moreover,total saponin also significantly increased the abundance of Sphingomonas,while high concentration of total saponin（90μg/g）significantly increased the abundance of Saitozyma and Ascochyta.6.Exogenous addition of two kinds of saponins mainly up-regulated the abundance of pathogenic fungi such as Kochiomyces,Rhodotorula and Ganoderma in bulk soil,and mainly up-regulated the relative abundance of Fusarium and Rhodotorula in rhizosphere soil.In the indoor culture experiment,four kinds of allelochemicals were added to co-culture with two strains of P.notoginseng root rot pathogens（Fusarium solani and Fusarium equiseti）to explore the effect of allelochemicals on the mycelial growth and spore germination activity of pathogens during co-culture.The results showed that 1.Vanillic acid and p-hydroxybenzoic acid could promote the growth of the mycelium of the two pathogenic and significantly promote the spore germination activity of the two pathogens.2.The total saponin promoted the mycelial growth of F.solani and F.equiseti on the 3d.At 96 h,the concentration of R₁at 80,120 and 180 mg/m L showed a significant promotion of spore germination.The concentration of total saponin at 5mg/m L（144 h）,100 mg/m L（36 h and 48 h）and 400 mg/m L（84 h）significantly promoted the germination of F.solani spores.In summary,phenolic acids and saponins promoted the proliferation and abundance of root rot pathogens by increasing the mycelial growth and spore germination activity of pathogens.