| Panax notoginseng is a kind of precious traditional Chinese medicine with high medical and economical value.However,root rot disease caused by rhizosphere microorganisms of P.notoginseng and accumulation of arsenic in P.notoginseng have seriously constrained the harvest and quality of P.notoginseng in yunnan province.Previous studies have found that some microorganisms isolated from the rhizosphere of P.notoginseng can inhibit the growth of pathogenic microbes of root rot disease and have been considered a promising approach in the prevention of root rot disease of P.notoginseng.At the same time,a lot of of studies have proved that certain microorganisms are capable of transforming the speciation of arsenic and further affect arsenic uptake by plants.However,whether the pathogenic microbes of root rot disease and biocontrol microbes isolated from rhizosphere of P.notoginseng can transform the speciation of arsenic and impact accumulation of arsenic in P.notoginseng plants is not known yet.Therefore,this study focused on two real problems related to P.notoginseng,i.e.arsenic accumulation and root rot disease control,and explored the impact of P.notoginseng rhizosphere microorganisms on arsenic speciation transformation and arsenic accumulation in P.notoginseng.This study aimed at providing fundamental data for the control of arsenic accumulation in P.notoginseng and the prevention of P.notoginseng root rot disease.In this paper,four pathogenic fungi,two biocontrol fungi and four biocontrol bacteria isolated from rhizosphere of P.notoginseng were selected from institute of microbiology,Yunnan University,these microorganisms were cultivated in culture medium that contained 100 mg/L As(V)and contained no arsenic,respectively.The growth condition of microorganisms under the two culture conditions were compared The bacterial liquid was detected by high performance liquid chromatography-hydride generation-atomic fluorescence spectrometry(HPLC-HG-AFS).The tolerance capacity of the microorganisms to arsenic and their arsenic transformation capacity were investigated by comparing the concentration of As(Ⅴ)and As(Ⅲ)in the culture medium by the end of cultivation.Once microorganisms from P.notoginseng rhizosphere with strong arsenic tolerance and arsenic transformation ability were identified,they were colonized in the roots of P.notoginseng that grew in soil artificially spiked arsenic concentration to 100 mg/kg.Around two months later,P.notoginseng plant tissues and the rhizosphere soil were harvested together.Total concentration of arsenic in soil and different tissues(roots,stems and leaves)of P.notoginseng was measured.The impact of colonized P.notoginseng rhizosphere microorganisms on the absorption,accumulation and transportation of arsenic in P.notoginseng were analyzed by calculating soil to root bioaccumulation factor(BCF)and transformation factor(TF)between different kinds of plant tissues.The main results of this study are the following:1.Three biocontrol bacteria,B.siamensis YIMPH10006、D.acidovorans YIMPH10032、B.formosus YIMPH10001,a biocontrol fungus,Trichoderma koningiopsis and a Pathogenic bacteria Fusarium flocciferum,grew well when exposed to 100 mg/kg As(Ⅴ)cultivation environment and they are good arsenic-tolerant bacteria.2.flocciferum and T.koningiopsis,have strong arsenic speciation transformation ability,only As(Ⅲ)was found in the culture solution.In biocontrol bacteria of root rot disease,D.acidovorans YIMPH10032 and B..formosus YIMPH10001had stronger arsenic reduction ability than B.siamensis YIMPH10006.As(Ⅲ)/[As(Ⅲ)+As(Ⅴ)l values were 0.94±0.04、0.89±0.03、0.72±0.05.These microorganisms may have genes related to arsenic transformation and efflux3.In this study,the total arsenic content in each kind of plant tissue of P.notoginseng decrease in the sequence of stem>leaf>root.In roots,stems and leaves,40%of the analyzed tissues samples had arsenic concentration exceeded 1 mg/kg arsenic concentration quality standard set for P.notoginseng,and total arsenic concentration of 5.6%of the measured plant samples was above 2 mg/kg arsenic concentration quality standard set for P.notoginseng4.There was no significant difference in the efficiency of arsenic uptake by root from soil among different rhizosphere microorganism treatment(p>0.05),arsenic enrichment coefficients in root of p.notoginseng were all less than 0.02.However,when comparing the arsenic uptake efficiency by P.notoginseng treated with microorganism with different arsenic transformation efficiency,the arsenic bioaccumulation efficiency of root from soil decrease in the following trend:strong +strong>strong + weak>strong>weak>no microbes.5.The transportation capacity of arsenic between different P.notoginseng plant tissues changed in the following trend:"root-stem">"stem-leaf’.The effect of rhizosphere microorganisms on the transportation process of arsenic is not significant.These microorganisms may not affect arsenic migration in P.notoginseng.Therefore,it can be inferred that the applying biocontrol microbes to control the root rot disease of P.notoginseng will not affect the transportaion process of arsenic within P.notoginseng. |
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