| Continuous cropping obstacles limit ginseng cultivation seriously, becoming a problem to be solvedimmediately of ginseng producttion。Microbial community composition was determined to investigate themicrobial ecology mechanisms of2root disease ginseng of continuous cropping obstacles, to explore therestoration effect and mechanisms of disease resistance and growth promoting effect. Related results andconclusions are listed as follows：1. Microbial ecology about the root zone soil of rusty root diseased and healthy ginseng suggestedabnormal microbial flora was the main cause of rusty root.(1) Diseased ginseng showed dwarf, much damage to yield and quality. The biomass, root weight andheight of plant and stem decreased by38.1%,35.9%, and34.3%,41.1%respectively.(2) The content ofavailable K and pH in rhizosphere of diseased ginseng plants decreased by19.2%and21.1%respectivelycompared with the healthy ginseng. It indicated that the content of available K and pH had relationshipwith incident of ginseng rusty root.(3) Microbial number and porporation varied significantly inrhizosphere soil and root surface soil. The number of bacteria and actinomycetes increased by224.5%and293.7%and the number of fungi decreased by42.6%in rhizosphere soil compared with healthy plants. Inroot surface soil, the number of bacteria and actinomycetes decreased by50.2%and49.8%respectivelywhile fungi were about650times more than healthy ginseng plants. The B/F(Bacteria/Fungi),A/F(actinomycetes/fungi) value in rhizosphere soil and root surface soil were about5times,6times and1310times,1280times respectively more than the diseased plants.(4) Soil microflora of diseased ginsengchanged. Harmful microbes Fusarium oxysporum were about31times more than healthy ginseng plantsand Pseudomonas aurantiaca increased54.1%compared with healthy plants in root surface soil. F.oxysporum and P. aurantiaca were24times and3times more than healthy plants in rhizosphere soil. Andbeneficial microbes Trichoderma asperellum did not isolated from diseased plants, Rhizobium giardiniiincreased by175.5%in rhizosphere soil and30times more than diseased diseased plants.2. Microbial ecology associated with healthy and diseased ginseng root of rust rot suggested the mainreason causing the rust rot of ginseng is the abnormal microflora of the soil in the root zone and surface.(1) The content of available K in rhizosphere of diseased ginseng plants decreased by11.3%comparedwith the healthy ginseng.There was no significant difference between healthy and diseased ginseng on thevalue of available NP, organic matter, soluble salt and pH.(2) The number of bacteria and actinomycetes in root zone decreased by99.7%,77.4%while fungi increased by36.3%, the B/F, A/F value of the healthyginseng decreased by99.8%,83.3%from the percentage composition of soil micorbes.(3) The number ofbacteria and actinomycetes in root surface decreased by57.8%和99.3%while fungi increased by128.5%,the B/F, A/F value of the healthy ginseng decreased5times and300times.(4) Colletotrichum pisi and F.oxysporum increased in diseased ginseng plants, but T. asperellum were isolated only in healthy roots. P.fluorescens and P. chlororaphis significantly lower than those in healthy roots compared with the diseased.3. Isolation of pathogen from rust rot and study of biological characteristics The phytopathogenicfungus Cylindrocarpon destructans was isolated from Tiande ginseng base in the south of Xiaoxinganlingmountain, Tieli, Heilongjiang. Colony grow well on PDA and CZA. The optimum carbon source andnitrogen source were sucrose and urea，the suitable pH value for mycelia growth was pH6~7, and theoptimum temperature was20-25℃.4. Study on actinomycetic ecology in soil with the different cultivating years in ginseng showed thequantity change of actinomycetes, especially antagonistic actinomycetes decreased, was correlated withsoil-borne diseases aggravation along with cultivating years.(1) The total actinomycetes and Stremptomyces were106×105CFU.g-1and193×105CFU.g-1of5years,41×105CFU.g-1and83×105CFU.g-1of7years respectively, there existed very significantdifference (P＜0.01); The number of Micromonospra and unidentified actinomycetes were11×105CFU.g-1and20×105CFU.g-1,54×105CFU.g-1and90×105CFU.g-1, significantly differently (p＜0.05).An increasing trend was taken between actinomycetes, Stremptomyces, Micromonospra and unidentifiedactinomycetes showed an increasing trend. Taoshan was similar to that.(2) Among271strains selectedfrom tested soil,108strains had antagonistic action to target pathogenic fungi of soil-borne diseases, being40%of isolated actinomycetes. In Taoshan, the antagonistic actinomycetes against5targets screened fromthe soil of1year were2.2-12times higher than that of5year indicating antagonistic actinomycetesdecreased along with the planting years.(3) Quantity and ratio of broad-spectrum antagonisticactinomycetes were as that. Flavus are the major genus among Streptomyces, which were4strains of15strong activity.(4) The percentage of antimicrobal actinomycetes to total actinomycetes had no relations totheir soil nutrients, but pH had.5. Screening and identification of antagonistic actinomycetes against ginseng rust rot and blightA total of578actinomycetes were previously isolated from Northwest soil and ginseng base inHeilongjiang.5strains of antagonistic actinomycete, which had obvious inhibitory effects on pathogenswere screened. Act11and Act12from Northwest soil showed more obviously inhibitory effects.5antimicrobial strains had strong inhibitory effects on the growth of pathogens by producing antibiotic andmutual effect between mycelia, such as winding and decomposition.6. Effect on growth, yield and quality of ginseng through the application of actimomyces agentActimomyces agent promoted ginseng growth and SPAD increasement, inhibit leaf spot disease development, improved plant defense related enzymes activity and increased root activity. Meanwhile,actinomycetes agent could have effect on impromoting the root weight, especially3,4-year-old ginseng asoptimum. Actinomycetes agent made the root volume, diameter, length and rhizoma length, weight trend toincrease. Four kinds of ginsenosides Rg1, Re, Rb1and Rb2of per root of3-year-old ginseng wereincreased respectively by84.9%,87.5%,77.3%and84.6%.7. The study on microecology mechanism of biological control agentsYield and quality of ginseng medicinal part improved, induced enzyme activities of leaves and rootactivity increased, and the number and proportion of bacteria and actinomycetes significantly increased butthe number and proportion of fungi decreased. Meanwhile, soil microflora was changed. Dominant bacteriaP. fluorescens, P. koreensis and Microbacterium oxydans in root zone soil and root surface soil were muchhigher than that in control. Pathogen Plectosphaerella cucumerina decreased in root zone soil and only wasisolated from control in root surface soil. |
PDF Full Text Request