The Effects Of Streptomyces TOR3209on Community Structure And Density Of Pear Culturable Endophytic Bacteira And Rhizobacteria

Pear is one of the main producing fruits in Hebei Province with a highadmiration in the wold. Recently, the phenomenon of sick or dead trees hascommonly appeared in old orchards, which has caused huge losses to fruit farmersand become a threat to the sustainable development of producing areas. Someresearches showed that this is associated with soil degradation, root rot, root-knotnematodes and root development defects occurred in the aging pear. Beneficialrhizosphere microorganism is one of the effective methods to restore the situation ofsoil degradation in old orchards. Streptomyces TOR3209, a kind of multifunctionalrhizobacteria, has played an important role in promoting plant growth, resistingdiseases and insects, salt-tolerance and relieving the toxin harm in root system. Thebacterial fertilizer developed basing on this strain has been used in some old pearareas, such as Zhao Xian and Jin Zhou. The bacterial fertilize shows remarkableimproving effectiveness in radication, recovering growth, yield and quality, and it iswell received by orchardists. However, the ecological mechanism is still unclear, andfurther researches are in urgency. In this work, we took the Streptomyces TOR3209asexperimental material and studied on the effects to dynamic changes about thecommunity structure and density of culturable plant endophytic bacteria andrhizobacteria during different growth periods. At the same time, the functionalidentification of the “contributing bacteria” was ongoing.By using the cultivable method and the rhizosphere soil models built in oldorchards, these bacterias were taken from root hairs, taproot, branches andrhizosphere during the flowering, early-fruiting, maturing and abscission period ofHuangguan pear with more than30years development applied bacterial fertilizerTOR3209or not. The16SDNA sequence analysis method was used to classify andidentify the status of the strains obtained, and analyze the dynamic changes of thecommunity structures and density. The plant endophytic bacteria and rhizobacteriawere screened by medium plate detection method, and many biological functions of the plant endophytic bacteria were tested, including antagonize pathogens, producesiderophore and IAA, dissolved inorganic phosphorus, organic phosphorus, andinorganic nitrogen. Biological assay has been used for the predominant strains. Theresults were as follows:1. There are421bacterias had been isolated from different tissues in pears duringdifferent growth periods, and they belong to38genus and80kinds of species,consisting of Bacillus21species, Brevibacillus4species，Paenibacillus3species,Pseudomonas7species, Curtobacterium3species， Microbacterium4species,Providencia2species, Agrobacterium2species and34kinds of other strains.Wherein, the bacterias numbered Q223and Q479were only97%similarity to otherclose bacteric in16SrDNA sequences, which suggested that they are likely to be twonew microorganism resources.2. After intruded by Streptomycetaceae TOR3209, the density and the diversityof community structure as well as the amount of functional bacteria in culturableendophytic bacteria and rhizobacteria had significantly increased in various tissuesduring different growth periods.(1) The total amount of plant endophytic bacteria and rhizobacteria weresubstantially increased. The quantity about bacterias during abscission period hasreached to significance level. During abscission period, amounts of the bacterias inhair roots, taproot, branches and rhizosphere were increased650.80%,122.22%,120.93%and611.54%respectively, which has extremely significance compared toother periods(p<0.01).(2) The population diversity of plant endophytic bacteria and rhizobacteria wasmarkedly enhanced. In abscission period, the species of bacteria were respectivelyincreased by40%,100%and28.57%in hair root, taproot and rhizosphere withTOR3209applied. But there were no significant changes in other periods.(3) In different tissues of pears, the amounts of conditioned pathogen for people,livestock and plants, such as Staphylococcus saprophyticus and Curtobacteriumflaccumfaciens were significantly reduced.(4) In various tissues of pears, the amounts of beneficial bacteria with different fuctions were significantly increased. The population of functional endophytes intaproot, which produced IAA and siderophore、dissolved organic phosphorus,have thenitrogen fixation and the ability to antagonize pathogens increased of21.95%,60.61%,57.14%,38.46%and36.59%. In hair root, the population of functionalendophytes which could antagonize pathogens and produced siderophore hadrespectively boosted by40.74%and31.71%. And the antagonistic pathogenic bacteriahad increased by28.57%in branch. The increase of beneficial bacterias was quitebeneficial for pear trees rapid recovering and reducing the diseases in roots, branchesand fruits.3. As test material, winter wheat was tested on Seedling growth promoting bystrains and six strains with obviously promoting growth function had been obtained,five of them were isolated from TOR3209treatment plants, including Bacillusmegaterium Q207, Bacillus megaterium Q210, Bacillus megaterium Q408, Bacillussubtilis Q410, and Bacillus mycoides Q452. These bacteria can germinate wheat seeds4hours earlier. Make plant and root fresh weight respectively improved by more than26.35%and33.81%, plant and root dry weight respectively increased by more than20.83%and31.26%.