Fusarium oxysporum causes the root rot disease of Polygonatum cyrtonema in China

Polygonatum cyrtonema, also known as Huangjing, belongs to the Liliaceae family and is a commonly used medicinal and edible plant in Asia. In recent years, P. cyrtonema root rot disease has frequently occurred in China, significantly impacting its yield and medicinal value. However, the pathogen of the disease has not yet been identified. In this study, we aimed to identify the pathogen causing the root rot disease of P. cyrtonema by applying morphological and molecular methods following Koch's postulates. Twelve fungal strains were isolated from nine diseased rhizomes of P. cyrtonema. Morphological analysis showed that the twelve isolates included eight colony types. Among that strain, HJ-5 has the typical characteristics of Fusarium oxysporum, including single-cell microconidia, chlamydospores, and sickle macroconidia. BLAST alignment and phylogenic tree based on the tef1, rpb2, β-tubulin, and ITS genes demonstrated that strain HJ-5 exhibits the highest similarity with Fusarium oxysporum. The strain HJ-5 is identified as F. oxysporum based on morphological and molecular characteristics. In addition, the pathogenicity test showed that among twelve isolates, only strain HJ-5 led to the rhizome softening and rotting on detached rhizomes and living plants of P. cyrtonema, consistent with symptoms observed in the field. To our knowledge, this is the first report on root rot disease in P. cyrtonema caused by F. oxysporum in China, which will provide a clear prevention and management target for the root rot disease of P. cyrtonema.