A Novel Endophytic Fungus Fusarium falciforme R-423 for the Control of Rhizoctonia solani Root Rot in Pigeon Pea as Reflected by the Alleviation of Reactive Oxygen Species-Mediated Host Defense Responses

Rhizoctonia solani root rot is a devastating fungal disease that causes significant yield losses in legume crops. A novel endophytic fungus Fusarium falciforme R-423 isolated from pigeon pea had a significant antagonistic capacity against R. solani. F. falciforme R-423 extracts could inhibit R. solani growth and cause it to die. Four host-specific and 15 genus-specific metabolites were identified as potential antimicrobial compounds. F. falciforme R-423’s inoculation effectively controlled R. solani root rot in pigeon pea seedlings and promoted root growth. Co-inoculation of F. falciforme R-423 and R. solani reduced the levels of oxidative stress, pathogenesis- and biosynthesis-related gene expression, and phenolic compound accumulation in roots compared to those infected with R. solani, confirming that reactive oxygen species-mediated host defense responses were alleviated due to the effective control of R. solani by F. falciforme R-423. Overall, F. falciforme R-423 was a promising biocontrol agent against R. solani root rot in legume crops.