Phytochemicals demonstrate potential fungicidal activity against Fusarium commune, a newly identified pathogenic fungus causing rhizome rot in Polygonatum cyrtonema (giant Chinese Solomon's seal)

Abstract

Polygonatum cyrtonema (giant Chinese Solomon's seal) is a perennial herb belonging to the family Liliaceae, with significant medicinal and dietary value. However, a severe rhizome rot has led to a decline in the yield and quality of this species. In this study, a fungus was isolated from symptomatic rhizome samples and identified as Fusarium commune through molecular and morphological analyses. In pathogenicity tests, the identification of F. commune as the causative agent of rhizome rot was confirmed by fulfilling Koch's postulates. Biological characteristics indicated that the optimal growth conditions for F. commune were a temperature of 25°C, pH of 8, carbon source of soluble starch, nitrogen source of peptone and a photoperiod of 24 h light. In order to reduce the use of chemical fungicides and explore natural substances to control the disease, the sensitivity of F. commune to seven phytochemicals was studied. Four phytochemicals (honokiol, 2‐allylphenol, magnolol and carvacrol) showed inhibitory activity, with honokiol having a 50% of the maximal effect concentration (EC50) of 9.99 ± 0.14 mg/L. The results of pot experiment showed that the four phytochemicals had significant control efficacy on the rhizome rot of P. cyrtonema, and the highest control efficacy was observed with honokiol. These findings provide a scientific basis for the control of rhizome rot in P. cyrtonema.