Effects and inhibition mechanism of phenazine-1-carboxamide on the mycelial morphology and ultrastructure of Rhizoctonia solani.

The purpose of this research was to explore the effect of phenazine-1-carboxamide (PCN) on Rhizoctonia solani and to elucidate its mechanisms of action. The toxicity of PCN to R. solani was measured using a growth rate method. The results indicated that PCN inhibited R. solani with a 50% effective concentration (EC50) of 9.0934μg/mL. The mycelia of R. solani were then exposed to 18.18μg/mL (2EC50) of PCN. Optical microscopy, scanning electron microscopy (SEM), and transmission electron microscopy (TEM) were used to observe the effects of PCN on mycelial morphology and ultrastructure. Following the PCN treatment, the optical microscopy observations revealed that the mycelia appeared twisted; the branching mycelia grew, but the main mycelia did not grow following branching; and the mycelial roots possessed more vacuoles. SEM observations revealed that the mycelia were locally swollen and exhibited a sharp decrease in prominence. TEM observations showed that the cell wall became thin and deformed; the mitochondria disappeared; the septum twisted; and most of the organelles were difficult to discern. Conversely, all of the organelles could be clearly observed in the control. We then used real-time quantitative PCR and an enzyme activity testing kit to further explore the effects of PCN on the cell wall and mitochondria. Physiological and biochemical results demonstrated that both the cell wall and mitochondria constitute are PCN targets. PCN inhibited the activities of chitin synthetase and complex I of the mitochondria electron transport chain. Molecular experiments demonstrated that PCN controlled the growth of R. solani mycelia by inhibiting the expression level of chitin synthetase genes. Future research on PCN should investigate its influence on metabolic pathways, thereby aiding in the potential development of novel pesticides.