Rhizosphere Microbial Community Diversity Of Radix Astragali And The Dynamic Changes Of Major Flavonoids Content

In order to study the rhizosphere microbial community composition difference of biennial Radix Astragalus and the dynamic changes of its four major flavonoids content among the development phase. We collected monthly samples from May to September in the experimental field, which located in chifeng city, Inner Mongolia province,2015. The content of calycosin-7-O-b-D-glycoside, ononin, calycosin and formononetin of five Radix Astragalus provenances (CF, LQ, HY, GS, and GY) was measured by the HPLC method. Meanwhile, its rhizospheric soil was collected to assess the microbial diversity in July and September. Besides, effects of progressive drought stress on Radix Astragalus rhizosphere microbial population and bimass also was explored.The experimental results are listed as following:1. With the advance of growth period, root dry weight, root length, plant height and root-cap ratio increased and calycosin-7-O-b-D-glycoside content increased gradually as well. In addition, the content of Radix Astragalus from different provenance also showed a certain differences. For instance, GS, higher than other provenance significantly, embodies a certain germplasm advance and other ingredients showed fluctuant trend. In addition, there is positive correlation between calycosin-7-O-b-D-glycoside content and plant height as well as dry weight. Hence, it is advisable to havest Radix Astragali in September.2. Rhizosphere bacterial community composition was similar in July and September, the dominant groups are mainly Arthrobacter, Streptomyces, Bacillus, Planomicrobium, Pseudomonas at genus level. Besides, two types of specific rhizospheric bacteria-Planctomycetes and Cyanobacteria were detected in July and September, respectively. Rhizospheric fungal community mainly consisted of Hypocreales, Pezizales, Agaricales, and unknown bacterial orders. Rhizospheric bacterial and fungal community structure similarity of Radix Astragalus was low compared to the control in July and September, whereas, the rhizospheric fungal community structure is of similarly highly among different provenance.3. Along with continuous drought stress, bacteria and actinomycetes amounts in the rhizosphere soil of Radix Astragalus first increased then decreased. However, the fungus amounts in the rhizosphere soil of A. mongholicus decreased continually comparing to the control. The biomass in aboveground and roots parts of Radix Astragalus, root and leaf tissue relative water content all declined but R/S-ratio increased with the increase of drought intensity. Correlation analysis showed that the number of rhizosphere soil microbe had a significant positive correlation with aboveground biomass but weakly related with roots biomass.