Control efficacy against rice sheath blight of Platycladus orientalis extract and its antifungal active compounds

Abstract

The control efficacy of Platycladus orientalis extract against Rhizoctonia sonali Kuhn, the causal agent of rice sheath blight, was evaluated by pot experiments under greenhouse conditions, and the antifungal compounds were isolated and identified through antifungal bioassay-guided fractionation using R. sonali as a tested fungus. The results indicate that the extracts from P. orientalis exhibited a significant reduction in the severity of rice sheath blight. The petroleum ether fraction partitioned from the ethanolic crude extract, showing the highest antifungal activity, was further separated, and two diterpenoid compounds with antifungal property, totarol and sclareol, were isolated and identified from the active subfractions. Totarol and sclareol possessed antifungal activity against most of the tested fungal pathogens of cereal crops such as R. solani, R. cerealis and Fusarium graminearum, indicating a similar broad antifungal spectrum. These findings suggest that the P. orientalis extract and its derived active compounds may be promising candidate agents for controlling plant fungal diseases like rice sheath blight.