Analysis Of The Bacterial Community Structure In Fumigants Reated Rhizosphere Soil And Diversity Of Endophytic Bacteria In Ginger

The research arranged experiment of ginger in qiujiadian, taian, Shandong province,including methyl bromide treatment, chloropicrin treatmen and no treatment and collectedrhizosphere soil sample at plant seedling stage, seedling stage, the earlier stage of stems andleaves vigorous, the later stage of stems and leaves vigorous, the earlier stage of rhizomeintamescentia stage and the later stage of rhizome intamescentia stage. Molecular biologymethods including T-RFLP and16s rDNA, combined with the methods CCA and RDA wereused to discuss the influence the rhizosphere bacteria community structure when we used thefumigant, and to study the genetic diversity of those ginger endogenous beneficial bacteriathat were screened out.The analysis of T-RFLP showed that, in ginger planting stage and seedling stage,microbial diversity of soil treated by fumigation agent was significantly lower than that ofsample without treatment. With this clarification: Using fumigation agent affect thecommunity diversity of ginger rhizosphere bacteria. While entering the vigorous growthperiod, fumigation agent effect recede gradually, the amount and type of microbes inrhizosphere soil begins to increase gradually through self-healing and other ways, microbialdiversity of soil recovery gradually, indicating that soil microbes has strong self-healingability. But when enter the later stage of rhizome intamescentia the microbial diversity ofusing fumigants processed ginger rhizosphere soil is still lower than that of sample withouttreatment, illustrate the use of the fumigants for some microbes in soil caused irreparabledamage, direct damage to the ginger rhizosphere micro ecological balance.As the analysis of the16S rDNA clone library result shows, during the growing seasonsof ginger in chloropicrin treated soil samples, the dominant colonies are Firmicutes andγ-Proteobacteria, and their percentages are21.1%and36.8%respectively. While these twobacteria do not have advantages in the soil which has not been treated by chloropicrin, instead,the advantageous colonies are Actinobacteria and Bacteroidetes which take up25.9%and37%respectively. Compared with those soil samples which have not been treated, there areno Actinobacteria and Gemmatimonadetes in those chloropicrin treated soil samples during the growing seasons while there are no Gemmatimaonadetes, Verrucomicrobia,Planctomycetes and Nitrospira during the seeding stage, and this illustrates that the use offumigant has influenced the colony structures in the rhizosphere soil of ginger seriously.Based on the physical and chemical properties of soil samples, we found that, in gingerplanting stage and seedling stage, in the soil treated by fumigation agent, the rate of humicdegradation and organic matter decomposition is much lower than without treatment, besidesavailable phosphorus, available potassium and trace elements of iron manganese copper zincaccumulation rate and accumulation were serious impacted. However using fumigantsinfluence the various mineral elements from the soil into each other seriously, not only affectthe normal growth of ginger, and easy to make the soil harden.We used the R2A culture medium to separate endogenous beneficial bacteria of gingersin order to study the distribution and population diversity of endophytic bacteria in gingerplants,248endophytic bacterial strains were isolated. Results indicated that the numbers ofendophytic bacteria of different growth stages ranged from10.4×104cfu/g FW to20.2×104cfu/g FW. Maximum bacteria numbers were obtained at seedling stage. A total of107functional strains were screened, including17antibacterial strains and90IAA-producingstrains. Based on ARDRA and16S rDNA sequences, these107strains were mapped to16genera. Bacillus and Pseudomonas were the dominant genera found. The present genera ofthe endophytic bacteria varied tremendously, with the highest species richness observed at theseedling stage. Sixteen strains were found to have antimicrobial activity against Pythiummyriotylum Drechsler, while seven strains were found to have antimicrobial activity againstPhyllosticta zingiberi Hori. Pseudomonas fluorescens, B. megaterium, and Enterobacterludwigii produced remarkably high levels of IAA. Only a few of endophytic bacterial strainswere inhibited in fresh ginger juice. Most of these strains were distributed during seedlingstage, including Roseateles depolymerans, Chryseobacterium taiwanense, E. ludwigii,Agrobacterium larrymoorei, P. fluorescens, and B. amyloliquefaciens. The results suggestthat the community of endophytic bacteria in ginger changes with the synthesis ofantibacterial substances, and ginger endophytic bacteria got adapted to those antibacterialsubstances such as flora gingerol. This study received a total number of107growthpromoting and antagonistic bacteria, and laid a solid foundation for the development ofdiscovering bacterial species resources.