Isolation and identification of Chaetomium globosum Y55 and its control effect against tobacco black shank in combination with dimethomorph

In order to screen biocontrol bacteria against tobacco black shank and enhance their control efficacy, antagonistic endophytic fungi against Phytophthora nicotianae were isolated from healthy tobacco tissues using the plate confrontation method and the one with the best control effect was identified. The antimicrobial spectrum and compatibility with dimethomorph of the strain were determined, and the control efficacy of its fermentation broth combined with dimethomorph against tobacco black shank was evaluated through indoor pot experiment. The results showed that a total of 37 antagonistic fungal strains against P. nicotianae were screened out. Among which strain Y55, identified as Chaetomium globosum based on morphological and molecular biological identification, exhibited the strongest inhibitory effect. The 10% C. globosum Y55 fermentation broth achieved an inhibition rate of 65.82% against P. nicotianae with a broad antimicrobial spectrum. The compatibility between C. globosum Y55 and dimethomorph was high and the inhibition rate of the combination of 10% C. globosum Y55 fermentation broth and 1.00 mg/L dimethomorph against P. nicotianae was 79.84%. In pot experiments, the treatment of the combination yielded a control efficacy of 70.95% against tobacco black shank, which was significantly higher than those of the single agent treatments.