Abstract: To explore high-efficiency biocontrol agents for tobacco Fusarium root rot, 11 fungal strains preserved in our laboratory were screened using the dual culture method, with Fusarium oxysporum and Fusarium solani as target pathogens. A highly efficient biocontrol strain, M14, was successfully isolated. Strain M14 exhibited plate inhibition rates of 79.10% and 79.31% against F. oxysporum and F. solani, respectively, and demonstrated broad-spectrum antifungal activity against five other pathogenic fungi, including Phytophthora nicotianae, with inhibition rates ranging from 42.06% to 100.00%. The cell-free fermentation filtrate of M14 inhibited spore germination of F. oxysporum and F. solani by 74.24% and 93.15%, respectively. Furthermore, its volatile metabolites significantly inhibited mycelial growth or sporulation of the pathogens. The plant growth-promoting effects of M14 were evaluated via seed soaking in spore suspension and root drenching with fermentation broth. Results showed that the spore suspension increased tobacco embryonic root length by 26.14%, while the 1.5-fold diluted fermentation broth increased the fresh and dry weights of potted tobacco seedlings by 25.52%—61.68%. Pot experiments demonstrated that M14 achieved biocontrol efficacies of 60.77% and 69.84% against root rot caused by F. oxysporum and F. solani, respectively. Based on morphological and molecular biological identification, strain M14 was identified as Trichoderma koningiopsis. These findings provide a theoretical basis and technical support for the development of biocontrol agents for tobacco Fusarium root rot.

Key words: tobacco Fusarium root rot, Fusarium spp., Trichoderma spp., inhibitory effect, growth promotion