Testing Of Seed-borne Fungi,development Of Rapid Molecular Detection Method And Control For Root Rot Disease In Panax Notoginseng

Panax notoginseng is a unique Chinese medicinal herb with high medicinal value and large market demand.However,the industrial development of P.notoginseng is seriously hindered by continuous cropping obstacles.Soil disinfection is an efficient and broad-spectrum pest control method,has remarkable effects on controlling soil-borne diseases,such as fungi,bacteria,nematodes and pests.It has been widely used in tomatoes,cucumbers,strawberries and other high value-added crops.However,it is seldom used in traditional Chinese medicinal crops.In this paper,a fluorescence quantitative PCR method was established to detect P.notoginseng root rot pathogen.The inhibition effects and mechanism of three fumigants on Fusarium solani were described.We also evaluated the biological efficacy of chloropicrin(PIC)and conducted a pyrosequencing-based analysis of 16S rRNA gene and internal transcribed spacer region to determine the bacterial and fungal profiles of PIC-fumigated soil. The main results are as following:1.The results of investigation on the seed-borne fungi of P.notoginseng showed that:Fusarium spp.is the main pathogens on the surface of P.notoginseng seeds,Plectosphaerella cucemerina represented main pathogens inside.The fungi isolated from the external surface and interior of seeds expressed significantly difference among the tested seeds2.F.solani was identified as a major pathogen causing P.notoginseng root rot.Phylogenetic analysis showed that these strains isolated from P.notoginseng belonged to two different specialization of F.solani,one ofthem is closely related to F.solani f.sp.radicicola3.Based on the TEF-1 alpha gene of F.solani,a pair of new primers was designed and a specific qPCR method for the detection of F.solani in soil was established.This method has good repeatability,high sensitivity and can detect at least 0.5 fg DNA or 1 conidia per gran of soil4.Indoor fumigation experiments showed that allyl isothiocyanate(AITC)and PIC exhibited good inhibitory activity against F.solani.Further detection of the respiratory intensity and ultrastructure of mycelial cells after fumigation revealed that AITC significantly inhibited mycelial respiratory metabolism,and both AITC and PIC could lead to plasmolysis,cell membrane rupture and the leakage of cytoplasm.5.Field efficacy experiment indicated that PIC could effectively control the soil-borne disease of P.notoginseng under the dosage of 30 kg per mu.The obstacles of continuous cropping of PR notoginseng were effectively solved and the yield of P.notoginseng increased significantly.6.The application of PIC had long-term effects on soil microbes.The number of harmful fungi such as Fusarium decreased,while beneficial fungi such as Trichoderma and Chaetomium increased.Pic had long-term effects on the diversity and structure of soil microbial community,and bacterial communities were affected more seriously by PIC than fungi.