Combined Use of Trichoderma atroviride CCTCCSBW0199 and Brassinolide to Control Botrytis cinerea Infection in Tomato

Tomato gray mold caused by Botrytis cinerea is one of the main diseases of tomato and significantly impacts the yield and quality of tomato fruit. The overuse of chemical fungicides has resulted in the development of fungicide-resistant strains. Biological control is becoming an alternative method for the control of plant diseases to replace or decrease the application of traditional synthetic chemical fungicides and genus Trichoderma is widely used as a biological agent for controlling tomato gray mold. Brassinolide (BR) is a plant-growth-promoting steroid. To enhance the efficiency and stability of Trichoderma activity against B. cinerea, an optimal combination of Trichoderma atroviride CCTCCSBW0199 and BR that controls B. cinerea infection in tomato was identified. Strain CCTCCSBW0199 was found to have antagonistic activity against B. cinerea both in vitro and in vivo. In addition, a fermented culture of chlamydospores and metabolites, or metabolites only of strain CCTCCSBW0199 also reduced growth of B. cinerea. BR reduced growth of B. cinerea and had no effect on the sporulation and growth of Trichoderma spp. An application of metabolites of a Trichoderma sp. + BR reduced gray mold on tomato leaves by approximately 70.0%. Furthermore, the activities of induced defense response-related enzyme, such as peroxidase, superoxide dismutase, catalase, and phenylalanine ammonia-lyase were increased in tomato plants treated with a Trichoderma sp. + BR. Our data suggested that applying a mix of metabolites of T. atroviride CCTCCSBW0199 + BR was effective at reducing gray mold of tomato and may lay a theoretical foundation for the development of novel biofungicides.