Levels of rhizome endophytic fungi fluctuate in Paris polyphylla var. yunnanensis as plants age

Paris polyphylla var. yunnanensis is an important medicinal plant with abundant saponins that are widely used in the pharmaceuticals industry. It is unclear why the levels of active ingredients increase as these plants age. We speculated that the concentrations of those components in the rhizomes are mediated by fungal endophytes. To test this hypothesis, we took both culture-dependent and -independent (metagenomics) approaches to analyze the communities of endophytic fungi that inhabit those rhizomes in plants of different age classes (four, six, and eight years old). In all, 147 isolates representing 18 fungal taxa were obtained from 270 segments (90 per age class). Based on morphological and genetic characteristics, Fusarium oxysporum (46.55% frequency of occurrence) was the predominant endophyte, followed by Leptodontidium sp. (8.66%) and Trichoderma viride (6.81%). Colonization of endophytic fungi was maximized in the eight-year-old rhizomes (33.33%) when compared with four-year-old (21.21%) and six-year-old (15.15%) rhizomes. Certain fungal species were present only at particular ages. For example, Alternaria sp., Cylindrocarpon sp., Chaetomium sp., Paraphaeosphaeria sporulosa, Pyrenochaeta sp., Penicillium swiecickii, T. viride, and Truncatella angustata were found only in the oldest plants. Analysis of (metagenomics) community DNA extracted from different-aged samples revealed that, at the class level, the majority of fungi had the highest sequence similarity to members of Sordariomycetes, followed by Eurotiomycetes and Saccharomycetes. These results were mostly in accord with those we obtained using culture methods. Fungal diversity and richness also changed over time. Our investigation is the first to show that the diversity of fungi in rhizomes of P. polyphylla var. yunnanensis is altered as plants age, and our findings provide a foundation for future examinations of useful compounds.