Study On Autotoxin-degrading Bacteria In Continuous Cropping Obstacle Of Panax Notoginseng

Panax notoginseng is a crucial rare Chinese traditional herb,poessing high medicinal value.Continuous cropping obstacle has been the bottleneck which restricts the sustainable development of P.notoginseng industry.One of the essential reasons resulting in continuous cropping obstacle is autotoxins.This paper studied the degradation of the crucial P.notoginseng autotoxins-ginsenoside by the dominant microorganism in rhizosphere soil of continuous cropping obstacle and main fungal pathogens,which would impove a new direction for degradation of P.notoginseng autotoxins and bioremediation of continuous cropping obstacle soil.Firstly,the dominant bacteria in the rhizosphere soil of continuous cropping and the effects of the degradation of the autotoxins were studied.By enriching the type of culture medium,the dominant bacteria and fungi in soil of un-planted,2 year diseased plant and 3 year diseased plant were isolated.The number of the bacteria and fungi isolates were 37 and 10 in un-planted soil,54 and 20 in 2-year diseased plant soil,61 and 15 in 3-year diseased plant soil individually.Results about the identification of all the isolates were described as following,there were 11 genus and 27 species in unplanted soil,11 genus and 29 species in 2-year diseased plant soil,10 genus and 37 species in 3-year diseased plant soil.4 genus,including Pseudomonas,Flavobacterium,Arthrobacter and Stenotrophomonas,were comman in all the samples.We obtained 8 ginsenoside degradation strains with tradational cuture method and 9 ginsenoside degradation strains with enrichment method.Stenotrophomonas maltophilia DSY2B8 and Pseudomonas chlororaphis DSY3B6 poessed the high degradation activity about Panax Notoginseng Saponins(PNS),especially ginsenoside Rb1.Secondly,the research of P.notoginseng root rot pathogens was carried out by traditional culture and qRT-PCR,and analysed the degradation effect of PNS futhermore.Two fungi isolates I.mors-panacis G3 B and F.solani DRF1 were obtained from root rot P.notoginseng samples abidingly.Pathogenicity test of them were verified in vitro and in vivo pot experiment,the results showed that they both caused the root rot disease.We established a rapid and accurate method for the detection of root rot fungal pathogens using qRT-PCR method based on the Histone H3 gene and verified the main position of Ilyonectria in the disease samples.The results showed that I.morspanacis G3 B and F.solani DRF1 both had the degradation ability of PNS,what was more,Ilyonectria mors-panacis G3 B had a high degradation effect on the ginsenoside Rb1.In summary,Stenotrophomonas maltophilia DSY2B8 and Pseudomonas chlororaphis DSY3B6 were the PNS degrading strains in all the isolates from continuous cropping obstacle soil of P.notoginseng.I.mors-panacis G3 B and F.solani DRF1,which were the main pathogenic fungi,had the high degradation ability of PNS.These stains may have the degradation ability of P.notoginseng autotoxins,which need to research further.