Effect Of Invasion Plant Solidago Canadensis L On Microflora Diversity In Rhizospheric Soil

Solidago Canadensis L. was initially introduced as an ornamental plant to Shanghai in 1935 in China, and spread to become a substantial and widespread sin one of the expansion of invasive plants in South China. Because of its powerful invasion capabilities, it will form a single dominant species in the invasion process gradually. In particular, Solidago belonging to the indigenous plants and its surrounding neighboring plants are unable growth, and reduced the diversity of the community, threat the ecosystem balance seriously and even give our country a certain amount of economic losses. So far it has become a problem to be settled urgently ecology.Past researches for Solidago canadensis focused primarily on morphological description, perniciousness, biological characteristics, quarantine and so forth, but it was infrequent for soil microecology.Therefore, as the subject investigated by invade Fujian province Solidago canadensis L. and Solidago this study measured their physical and chemical properties of rhizosphere soil, the three major rhizosphere soil microorganism changes in microbial flora, and through application of two molecular biology technology T-RFLP and DGGE, the present focuses on an in-depth comprehensive analysis for soil microbial bacterial community structure and function. From the point of the soil micro-ecology, we study invasion mechanism of Solidago Canadensis L. The results showed that:(1) Rhizosphere microbial population of Solidago Canadensis L. happened visible changes.Through traditional training methods, we analyse the quantity changes for bacteria, actinomycetes and fungi of three soil samples by plate count method, and can be seen: in the three soil types, bacteria occupy the largest proportion, with the CK comparison, Solidago Canadensis L. rhizosphere actinomycete increase. It shows that Solidago Canadensis L. has a certain promote role on soil actinomycete, oppositely, Solidago are no such trends. Two Solidago compared with CK, bacteria and fungi increased in quantity. This kind of change of microbial quantity can be sensitive to reflect changes in soil quality of the environment and soil biological activity.(2) Rhizosphere bacterial community diversity of Solidago canadensis L.were reduced,the imbalance between species may be related to allelopathic substances of root exudates.Terminal restriction fragment length polymorphism (T-RFLP) analysis showed that rhizosphere soil bacterial community diversity of Solidago canadensis L. had been changed markedly. Invasive species plant dominant species of Solidago canadensis L. was changed, and indigenous species had not been changed. The subdominant species of invasive species and indigenous species are Bacillus, but lower than CK, subdominant species of Solidago canadensis L. had the greater rate of increase is 1.67 times that of indigenous species, compared on the dominant species, it occupied a considerable proportion . The antibiotics produced by metabolic processes of Streptomyces in Solidago canadensis L. can inhibiti the growth and sharp increase of subdominant species, and resulting in decreased for bacterial species diversity, which may be the reasons for invasive plant Solidago canadensis L. formed a single species gradually.Denaturing gradient gel eleetrophoresis (DGGE) analysis showed that the invasive species Solidago canadensis L. caused decline in the diversity of bacterial species, the number of changes happened mostly uncultured (Uncultured) bacteria. In the sequence alignment results, Sequence homology of the culture bacteria Chelatococcus sp.and Hyphomicrobium sp. reached 95%, and had the largest dominant species number, compared with CK, the uncultured (Uncultured) bacteria of Alphaproteobacteria decrease. Hyphomicrobium sp. are antinitrobacteria and can been available nitrogen and phosphorus removal, and utilize methanol as a carbon source. And Chelatococcus sp. can degradation polycyclic aromatic hydrocarbons are highly effective strains. We can only surmise that the emergence of the dominant species bacteria may be linked to Allelochemicals of Solidago canadensis L. root exudates. the decrease of diversity may be caused by accumulated in these root exudates of the soil.(3) Complementary technologies of T-RFLP and DGGE molecular ecology.In T-RFLP analysis, dominant species of Solidago canadensis L. rhizosphere soil are actinomycete species, and in DGGE analysis also detected Actinomyces species (41 bands) and increase than the other two soil samples. In addition, two molecular ecology detected all the dominant species are Alphaproteobacteria in CK soil and indigenous species soil. These results illustrate the consistency of two techniques in molecular ecology studies for rhizosphere microbial community structure changes in the accuracy.In addition, DGGE analysis detected a lot of sequence homology higher with the Hyphomicrobium sp of Alphaproteobacteria., whereas in T-RFLP did not detect the case of bacteria; T-RFLP analysis detected much more bacterial species than DGGE analysis. These conclusions also shows that the two molecular ecology means are complementary. Synthesizing the experimental various results, we can see: after Solidago canadensis L. invade some particular environment, the rhizosphere soil microorganism happened obvious changes. Through traditional training methods to study three kinds of soil microorganisms, we can see: soil bacteria in three soil have also accounted for the largest proportion, and the increase number of rhizosphere actinomycete Solidago canadensis L. shows that Solidago canadensis L. must have a auxoaction on soil actinomycete, the situation in Solidago does not exist. Two non-culture methods that T-RFLP and DGGE technology on the three soil rhizosphere microbial analysis showed that: Solidago canadensis L. rhizosphere soil bacterial community diversity decreased significantly. Advantage species of Solidago canadensis L. rhizosphere soil bacterial community had changed, and indigenous species had not changed. Subdominant species of invasive species and indigenous species are Bacillus strains gang, subdominant species of invasive species Solidago canadensis L. occupy a considerable proportion like advantages species. The substantial emergence of genus Streptomyces of Solidago canadensis L. as well as the sharp increase in quantity of subdominant species resulted in the decreased diversity of bacterial species, and this may be the reason for the invasive plant Solidago canadensis L. formed a single advantage species gradually. These bacteria in quantity change happened are uncultured bacteria mostly. Advantage species in Solidago canadensis L. Chelatococcus sp. and Hyphomicrobium sp.'s existence may be closely linked to Solidago canadensis L. root exudates in Allelochemicals. The decrease in diversity may be caused by these accumulated root exudates in the soil. Two non-culture technology, making experimental results have been consistent, to some extent, improved the accuracy study of the rhizosphere soil microbial diversity and established a foundation for future more in-depth research on soil microbial.