Effect Of Ginsenoside On Chemotaxis Aggravation Of Soil Rust Rot In Continuous Cropping Soil And Its Mechanism

The Ginseng(Panax ginseng C.A.Mey.)known as "the king of herbs".It takes 30 years for ginseng to be planted in the same soil before it can be planted again,otherwise it will lead to production reduction or even no harvest.Continuous cropping obstacle has become an important factor in restricting ginseng production.Finding allelopathic substances that cause continuous cropping of ginseng has been a research hotspot,Triterpenoids saponins,as the special substances of ginseng plants,have been paid much attention.However,previous studies mainly focused on the autotoxicity effect of triterpenoid saponins on ginseng plants.Systematic studies on the chemotactic response of triterpenoid saponins to soil microbial population structure and pathogenic microorganisms and their pathogenic mechanism were rarely reported.This study explored the effect of total ginsenosides on soil microbial population structure,and explored the dose-effect relationship and action law between ginsenosides and soil microbial population.In order to explore the chemoattractant response of triterpenoid ginsenosides to ginseng rust rot bacteria and its pathogenic mechanism,ginseng rust rot bacteria,which is the most obvious pathogen of ginseng continuous cropping disorder,were selected as the research object,and the transcriptional regulation mechanism of ginsenoside Rg1 response by ginsenoside rust-rot bacteria was studied by high throughput omics.The aim is to provide scientific basis and technical support for finding the cause of ginseng continuous cropping disorder.The main findings are as follows:(1)The total ginsenosides significantly changed the bacterial community composition in the new forest soil.The bacterial composition of soil samples treated with different concentrations of ginsenoside was significantly different,and the bacterial microbial community showed significant gradient changes with the increase of ginsenoside concentration,and there were significant differences at different time points under the same treatment concentration.At the phylum level of the soil bacterial community,the patterns of each treatment were very similar at the 10-day,50-day and 90-day time nodes.With the increase of the total ginsenoside concentration,the relative abundance of the level bacteria in the new forest soil decreased significantly.These results demonstrated that ginsenoside treatment reduced the relative microbial richness compared with the control group.(2)The total ginsenosides significantly changed the fungal community composition in the new forest soil.The results showed that the concentration of ginsenosides was 10mg/L on the90 th day of total ginsenosides treatment had the greatest effect on the relative abundance of family compared with the control group.There were significant differences between the control group and the total ginsenoside treatment group at the same time node.On day 10,about 38% of the order level in the control group were richer than those in the ginsenoside group.With the increase of treatment time,this value continued to increase,and about 42% of the order level in the control group on day 50 was richer than those in the ginsenoside treatment group.About69% of the order level in the control group at day 90 were richer than those in the ginsenoside group.The relative abundance of harmful fungi such as Fusarium,Neonectria,Penicillium,Trichoderma,and Neocosmospora increased significantly after total ginsenoside treatment and peaked at day 90.(3)The Ilyonectria robusta have a chemotactic response by ginsenoside.Ginsenoside,ginsenoside Rg1,ginsenoside Rb1,ginsenoside Rc and ginsenoside Re were all positively chemotactic.The chemotactic effect of ginsenoside Rg1 on ginsenoside Rg1 was the strongest,and the optimal chemotactic parameter was concentration of 1mg/L,p H of 7,and temperature of25 ?.The optimal chemotactic concentration of ginsenoside Rb1 and ginsenoside Rb1 by ginsenoside rust-rot bacteria was 10mg/L,and the optimal chemotactic concentration of ginsenoside Rg1,ginsenoside Re and ginsenoside Rc was 1mg/L.The optimal chemotactic p H of ginsenoside,ginsenoside Rg1 and ginsenoside Rc by ginsenoside rust rot bacteria was 7,and the optimal chemotactic p H of ginsenoside Rb1 and ginsenoside Re was 8.The optimum chemotactic temperature for 5 kinds of chemotactic solution of ginseng rust rot bacteria was25?.Compared ginseng rust rot fungus pathogen spores under the condition of the optimal parameters of chemotactic by 5 kinds of the chemotactic fluid under the stimulus of all appear the phenomenon of the spore germination rate increases,the ginseng saponin Rg1 chemotactic liquid spore germination rate is highest,2.51 times that of the control group,the second is the chemotaxis of ginseng total saponins and ginseng saponin Re fluid,the spore germination rate,respectively 2.11 times and 2.18 times that of the control group;Under the optimal chemotactic conditions,the growth rate of mycelia of ginseng rust rot bacteria under the influence of five chemotactic solutions increased with the increase of culture time.The chemotactic growth rates of ginseng rust rot bacteria reached the maximum on the 4th day of the culture of 5 chemotactic solutions,which were 0.435,0.526,0.398,0.375 and 0.402,respectively.The chemotactic growth rate of ginsenoside Rg1 chemotactic solution at days 3,4 and 5 was significantly higher than that of other 4 chemotactic solutions(P < 0.05).The dry weight of mycelia in totalginsenoside,ginsenoside Rg1,and ginsenoside Rc chemotactic solution of ginsenoside was significantly higher than that in the control group(P < 0.05).(4)Ginsenosides significantly affected the occurrence of rust rot and the activity of cell wall degradation enzymes in ginseng.A high concentration of ginseng total saponins(100mg/kg dry soil),low concentration of ginseng saponin Rg1(20 mg/kg dry soil)and high concentration of ginseng saponin Rg1(100 mg/kg dry soil)treatment group and old ginseng soil pot set(LSD)are of a similar result shows that under the condition of potted ginseng total saponins and ginseng saponin Rg1 processed ginseng plant appeared similar to ginseng continuous cropping obstacle phenomenon.In the process of ginseng rust rot fungus infection ginseng in 35 days pectin methyl trans(PMTE)to eliminate enzyme activity began to increase ginseng rust rot fungus began to destroy the ginseng cells around the pectic substances,and treatment group improved the ginsenosides pectin methyl trans eliminate enzyme activity(PMTE)to speed up the ginseng rust rot fungus infection,exactly 40 days of cellulose enzyme(Cx)began to play a leading role,and HT,LRg1 and HRg1 treatment group(Cx)of cellulose enzyme activity of ascension,accelerated the ginseng rust corrosion of ginseng materials such as cellulose decomposition,thus to speed up the ginseng rust rot fungus infection.(5)Ginsenoside Rg1 regulates the gene expression of ginsenoside rust-rot fungus.Rg1 processing ginsenosides of ginseng transcriptome sequencing found that are differentially expressed genes in the ABC transporters(ABC transporters)significantly enriched in C3 vs G3 enrichment degree in comparison group was significantly lower than comparison group,other time points that ginseng rust rot fungus during induction of signal transduction in short-term Rg1 play a bigger role,but with the increase of Rg1 induction time,effect gradually reduced.In comparison with the database of genes related to host plant-pathogen interaction,26 highly matched(> 80%)genes were found to be differentially expressed with Rg1 cultured ginseng rust rot bacteria.It mainly includes Cfmc,Boaa,Vtlr,Vatr1,Famyo2,Mosfa1,Groel,Eprs,Fsr1,Tsr,Thioredoxin 1,Cspv,etc.,among which 10 genes are related to the weakened toxicity of pathogenic bacteria,accounting for 38.5% of all 26 genes,3 genes related to the loss of pathogenicity accounted for 7.7%,and 1 gene related to the increase of virulence accounted for3.8%.These results indicate that ginsenoside Rg1 influences the interaction between ginseng plants and ginseng rust rot bacteria through a variety of mechanisms,including the change of pathogenicity.In conclusion,the total ginsenosides significantly reduced the relative abundance of soil microbial population,which was positively correlated with the treatment time and treatment concentration.High concentrations of ginseng total saponins,low concentration Rg1 ginsenosides,high concentrations of ginseng saponin Rg1 and high concentration of Re ginsenosides can significantly affect the ginseng rust rot fungus(Ilyonectria robusta),and to promote ginseng rust rot fungus mycelia growth,spore germination and mycelial dry weight of indicators,such as different time node in ginseng rust rot fungus infection ginseng significantly higher cellulose enzyme(Cx),pectin methyl trans eliminate enzyme(PMTE)and galacturonic acid polymer trans(PGTE)to eliminate enzyme activity,speed up the ginseng rust rot fungus infection.Ginsenoside Rg1 can affect the pathogenic ability of ginsenoside Rg1 by affecting the signal transduction and pathogenicity of ginsenoside Rg1.