Microflora diversity analysis of R.rehmannia rhizospheric soil in different monoculture years

• 1、Institute of agricultural ecology of Fujian Agriculture and Forestry University

Abstract：The rhizospheric soils sampled from the four different plots, including the newly planted, the two-year monoculture , the wild R. glutinosa and the control, were used to study the biomass and shifts of soil microflora by PLFA and T-RFLP analysis. It was observed that the wild R. glutinosa under continuous monoculture were small and weakening, unable normal growth, withered and ultimately died, while the wild R. glutinosa and newly planted were able to grow normally and no plant diseases and insect pests appeared. PLFA analysis indicated that the microbial community structure was significantly different among the wild R. glutinosa rhizospheric soils with different years of monoculture. There was relative consistency between wild R. glutinosa rhizospheric soil and new planted wild R. glutinosa soil. Compared with R. glutinosa rhizospheric and new planted soil,The ratio of bacteria/fungus in two-year monoculture soil declined. Furthered analysis by T-RFLP suggested that there were some diference in bacterial comunity structure of R. glutinosa rhizospheric soils. It was found that the bacteria belong to Proteobacteria and Firmicutes were predominent in the wild and newly planted R. glutinosa soils. Some beneficial biocontrol bacteria (such as Bacillus, Pseudomonas, etc) gathered in the rhizosphere of wild and newly planted R. glutinosa, however a large number of pathogenic bacteria bred in the rhizospheric soil of the two-year monoculture R. glutinosa, such as Clostridium, Flexibacter polymorphus, Clostridium ghoni, etc, and which went anainst the colonization of beneficial bacteria and cellulose degradation bacterium. For further study, qRT-PCR analysis verified that the total number of pseudomonads was much higher in wild and newly planted R. glutinosa soils than in two-year monoculture soil. In conclusion, wild R. glutinosa monoculture exists consecutive monoculture problem as well. And the pathogenic microbes bred seriously in the rhizospheric soil of wild R. glutinosa under the monoculture regime, and yet the number of beneficial bacteria declined, which weakened the ability of wild R. glutinosa to resist the disease so that the two-year wild R. glutinosa grew abnormally and the yield decreased drastically.

Keywords： Rehmannia glutinosa, PLFA, T-RFLP, Microbial diversity, plant rhizosphere