The characters of root-derived fungi from Gentiana scabra Bunge and the relations with their habitats

Gentiana scabra Bunge (gentian) is one of the best-known traditional Chinese medicinal plants and its dry roots and rhizomes are usually used as medicine. To our knowledge, the main active metabolites of gentian, such as gentian polysaccharide and gentiopicroside, determine the quality and pharmaceutical effect of gentian. The root-derived fungi including endophytic fungi and rhizosphere fungi are key factors which affect the secondary metabolism and the utilization of soil nutrients of gentian. Therefore, it is necessary to investigate the characteristics and dynamics of root-derived fungi related to gentian, as well as their relationships with the quality of gentian. The population, diversity, and the dominant type of endophytic and rhizosphere fungi in gentian were determined by using ITS rRNA gene amplicon and sequencing methods. The potential influences of different habitats on fungi communities and the correlation between fungi communities, the main active metabolites of gentian and soil physicochemical properties were analyzed by statistical methods. The population and diversity of endophytic and rhizosphere fungi varied with both habitats and growth stages, showing a significant difference. Among them, the predominant genera of endophytic fungi were Lecidella, Leptoshaeria and unclassified_p_Ascomycota with the relative abundance of 35.1%, 9.0% and 7.3%, respectively, while the predominant genera of rhizosphere fungi were complicated. Compared to endophytic fungi, the diversity of rhizosphere fungi was obviously affected by soil physicochemical properties, including pH, water content, alkali hydrolysis nitrogen (AN), available phosphorus (AP), etc. Additionally, we found that the accumulation of gentiopicroside was positively correlated with endophytic fungi of Epicoccum and rhizosphere fungi of Mortierella, Solicoccozyma, Talaromyces and Trichoderma. The accumulation of gentian polysaccharide was negatively correlated with endophytic fungi of Lenzites, Mucor, Myrothecium and Saccharomycopsis and rhizosphere fungi, such as Botrytis, Cadophora, Cladophora, Didymela, Fusarium, etc. In this work, the differences on population, diversity, and the dominant type of endophytic fungi and rhizosphere fungi in gentian were revealed. The relationship between the main active metabolites of gentian and root-derived fungi, and the relationship between soil physicochemical properties and root-derived fungi were clarified, respectively. It is believed that our work will guide to explore strategies on improving the quality of gentian by regulating soil factors and root-derived microbial community structure with microorganisms.