Analysis Of Continuous Cropping On Rhizosphere Microbial Community Structure In Ginger Field

To study the relationship of the ginger rhizosphere microbial community and thecontinuous planting years, and discuss the distribution and diversity of antagonistic bacteriaaround ginger rhizosphere, ginger rhizosphere soil were sampled at the rhizome enlargementstage in different fields, namely, planting one year, two years, four years, six years, eight yearsand eleven years. Samples were collected in Anqiu city and numbered DM1, DM2, DM4,DM6, DM8, DM11. Use Terminal Restriction Fragment Length Polymorphism (T-RFLP), theDenaturing Gradient Gel Electrophoresis (DGGE), the construction of16S rDNA clonelibrary and the Principal Component Analysis (PCA) methods for discussing the mechanismof ginger continuous planting obstacle.The Shannon indexes based on the T-RFLP fingerprints were compared: DM1>DM2>DM4>DM6>DM11. Sixteen T-RFs were gradually reducing or disappeared with the growthof planting years, and these T-RFs had strong and positive correlations with H, pH and Zn.Four T-RFs were gradually increasing or appeared, while these T-RFs had strong and positivecorrelations with OM, NN, K, P, AN, Mn, Fe, Cu in the environment. According to differentbiological functions, the dynamic T-RFs were associated with carbon cycle, nitrogen cycle,sulfur cycle, soil quality improvement, pathogens inhibitions and pathogenic bacteria. Besides,We respectively calculated the diversity indexes based on DGGE fingerprints, and found theShannon indexes of bacteria were compared: DM1>DM2> DM4>DM6>DM8>DM11, whilethose of fungi were DM1<DM2<DM4≈DM6<DM8<DM11. According to the comparationwith the similarity coefficients of DGGE, DM1, DM2, DM4and DM6samples wereobviously clustered into one group, while DM8and DM11samples were the other.Results showed that the ginger rhizosphere bacterial community consisted of α-Prote-obacteria (14.53%), β-Proteobacteria (17.13%), δ-Proteobacteria (14.31%), γ-Proteobacteria(3.49%), Acidobacteria (12.03%), Planctomycetes (1.52%), Bacteroidetes (5.79%), Firmicu-tes (6.76%), Verrucomicrobia (1.70%), Nitrospira (1.64%), Chloroflexi (3.17%), Gemmatim-onadetes (2.78%), Cyanobacteria (0.83%) and Actinobacteria (2.50%) and unclassfied bacte- ria (11.81%).19816S rDNA sequences, obtained from six clone libraries, were classified into14phyla in principle. The outcomes based on16S rDNA library construction also attested thatginger rhizosphere bacteria community gradually had become more simpler and monotonous.In the paper, we screened42,25,30rhizosphere antagonistic strains by the method offlat-panel confrontation, respectively with ginger pythium myriotylum drechsler pathogen,leaf spot pathogen and ralstonia solanacearum pathogen as target microbes. The main groupsand genetic diversity of rhizosphere antagonistic strains were examined by ARDRA analysisand16S rDNA sequence analysis methods. The results showed that the antagonistic activity isobvious and antagonistic strains have great genetic diversity. ARDRA revealed that, on80%similarity level, the antagonistic strains against pythium myriotylum drechsler pathogen wereclustered into12groups, and the antagonistic strains against leaf spot pathogen were clusteredinto10groups, and the antagonistic strains against ralstonia solanacearum pathogen wereclustered into10groups. All the rhizosphere antagonistic strains belonged to Bacillus,Pseudomonas, Paenibacillus, Brevibacillus and Enterobacter.In all, the ginger rhizosphere microbial community structure of the short-term continuouscropping years (1~6years) changed little, but the newly forming commubity contained morefungal species and less benificial bacterial species for soil health and fertility quality aftereight years. It is the important reason that results in the ginger continuous obstacle. Besides,ginger rhizosphere are rich in antagonistic bacteria.