Screening of antagonistic fungi against web blight disease and identification of volatile metabolites produced by Trichoderma

Aerial web blight caused by Rhizoctonia solani is one of the main soil borne pathogens which infects soybean crops. Biological control using antagonistic fungi has been reported promising to reduce the incidence of this disease. This study aimed to determine antagonistic activity of Trichoderma virens and T. asperellum against R. solani and to investigate total phenolic changes in soybean plants which interact with those Trichoderma in infected soil. Volatile metabolites produced by Trichoderma were also detected and identified. Antagonistic activity of five isolates of T. virens and five isolates of T. asperellum were comparable; the ranges of in vitro antagonistic activities were 88.7-99.6% and 85.7-91.3%, respectively. Both Trichoderma were able to reduce R. solani infection. Disease intensities of 22-40% and 24-40% for T. virens and T. asperellum were observed lower than that of control (> 50%). The increase of total phenolic and flavonoid contents depended on Trichoderma isolates. Volatile compounds were detected in both Trichoderma. Isolates of T. asperellum (F isolate) and T. virens (E isolate) triggered the increase of total phenolic contents which could be potential for biological control agents to induce systemic resistance in soybean.