The Inhibitory Effect of the Plant Alkaloid Camptothecin on the Rice Sheath Blight Pathogen Rhizoctonia solani

The rice sheath blight caused by Rhizoctonia solani is one of the most destructive diseases of rice worldwide.Present study presented the inhibitory effect and mechanism of the plant alkaloid camptothecin on R. solani.Results indicated 14.32, 34.88, 59.94, 68.54, 76.38 and 77.72% inhibition of mycelial growth after 48 h of incubation at 6.25, 12.50, 25.00, 50.00, 100 and 200 μg/mL camptothecin.The soluble protein content in mycelia was significantly increased, the N-acetyl glucosamine content and chitinase activity was significantly reduced, but the sugar content was unaffected by camptothecin at 100 μg/mL after 12 h and 24 h treatment.Moreover, the optical microscopic and transmission electron microscopic observation revealed that the fungal mycelia are sparse with a loose structure, mitochondrial nule3mber, and morphological characteristics of camptothecin-treated R. solani.Overall, the antifungal activity of camptothecin against R. solani, suggested that camptothecin has a great potential in the control of rice sheath blight.