Identification and fungicide sensitivity of Fusarium cugenangense associated with root rot disease of Polygonatum cyrtonema Hua in China.

Polygonatum cyrtonema Hua is a valuable medicinal herb widely cultivated in China, but its production has been severely threatened by root rot disease. In this study, pathogenic fungi were isolated from diseased rhizome samples collected in Huaihua City, Hunan Province, and identified through morphological characterization, multi-locus phylogenetic analysis, and pathogenicity tests fulfilling Koch's postulates. In this study, isolate HJBK 4-6 of Fusarium cugenangense was identified as a causal agent and is reported here for the first time associated with root rot on P. cyrtonema Hua in China. In vitro fungicide sensitivity assay revealed that ethylicin exhibited the strongest inhibitory activity against mycelial growth of F. cugenangense (isolate HJBK 4-6) (EC50 =0.92 μg/mL), achieving 100% inhibition at 2.5 μg/mL, followed by chlorothalonil (EC50 =2.34 μg/mL, with a maximum inhibition of approximately 78%). In contrast, pyraclostrobin and osthole showed poor efficacy, with EC50 values of 19.56 μg/mL and 18.23 μg/mL, respectively. This study provides a preliminary reference for disease diagnosis and fungicide screening, but field application recommendations will require further validation through greenhouse and field trials with a broader range of isolates.