Study On The Relationship Between Root Microbiome And Main Compounds In Dendrobium Officinale

Dendrobium officinale Kimura et Migo is traditional and precious medicinal plant of Orchidaceae in China.It depands on mycorrhizal symbiotic relationship with fungi to get seed germination and seedling growth under natural conditions.D.officinale mainly contains compounds such as polysaccharides,flavonoids,and astragalus.In China,wild D.officinale is mainly distributed in Anhui,Zhejiang,Yunnan,Guizhou province etc.Due to the harsh growth environment,coupled with excessive collection,wild D.officinale is on the brink of depletion.In recent years,there are many industrial bases were developed of D.officinale by the application of plant tissue culture technology.However,the quality of medicinal D.officinale has declined using tissue culture seedling propagation and how to improve the quality of cultivated D.officinale is extremely urgent.In the past two decades,research on the relationship between orchids and fungi has mainly focused on the diversity,distribution,and biological activity.However,there have been few reports on the relationship between microorganism and the accumulation of chemical components in D.officinale.Therefore,the study of the role of microorganisms in the quality formation of D.officinale is particularly important for the improvement of medicinal quality and the development of the Orchidaceae medicinal plants industry.This study collected 3-year old D.officinale cultivated in greenhouse from 15 main areas,and analyzed the composition of its endophytic fungi and rhizosphere bacterial communities.Phenol sulfuric acid and HPLC were used to determine the content of polysaccharides and flavonoids of D.officinale.Correlation analysis was used to analyze the relationship between microbial community and effective components.At the same time,combined with the coculture experiment of orchid mycorrhizal fungi(OMF)and seedlings of D.officinale,we verified that OMF could effect the accumulation of polysaccharides and flavonoids of D.officinale.The main findings are as follows:1.The microbial groups with higher abundance include Nectriaceae and Sebacinaceae,etc.There are 9 OMF groups,accounting for 3.00%of the total sequences of endophytic fungi,including Serendipitaceae,Sebacinaceae,etc.The rhizosphere soil bacteria of D.officinale are mainly composed of Proteobacteria,Actinobacteriota,etc.The microbial diversity in Zhejiang and Guangdong province is higher(fungal shannon index is 2.79 to 3.02,bacterial shannon index is 5.28 to 5.85);the microbial diversity in Yunnan and Chongqing province is lower(fungal shannon index is 1.29 to 2.01,bacterial shannon index is 4.72 to 5.07).2.The content of polysaccharides and flavonoids in D.officinale from different regions were determined.The content of polysaccharides and flavonoids in D.officinale in Guangdong and Zhejiang province is higher than that in other regions(the average polysaccharide content is 29.71%,and the average flavonoid content is 694.97μg/g).It will provide data support for the determination of polysaccharides and flavonoids in D.officinale cultivated nationwide.3.By analyzing the correlation between the content of polysaccharides and flavonoids and its root microbial composition,we found that the content of polysaccharides was significantly correlated with Hyaloriaceae,Aspergillaceae,Pseudolabrys and Roseiarcus;the content of flavonoids was significantly correlated with Ceratobasidiaceae,Serendipitaceae,Sphingomonas,Rhodoplanes,etc.Combined with the results of high-throughput sequencing,we defined core fungal microbial groups include:Nectriaceae,Aspergillaceae,etc;the core bacterial microbial groups include Proteobacteria,Actinobacteriota,etc.4.Finally,we co-cultured the representative strains of culturable fungi found in the root of D.officinale based on high-throughput sequencing with D.officinale seedlings,and found that orchid fungi can promote the growth of D.officinale seedlings and the accumulation of flavonoids content,which showed that symbiotic fungal groups were significantly related to the content of flavonoids in D.officinale.This study revealed the diversity of the root microbe of D.officinale in different regions,and found that microorganisms were significantly correlated with the content of polysaccharides and flavonoids.This conclusion was verified through symbiotic experiment.The results of this writing will serve as reference for the study of the relationship between microorganisms and the formation of medicinal plants.At the same time,it also lays the foundation for utilizing beneficial microorganisms for the artificial cultivation of high-quality D.officinale.