biological inhibition of thuja collar and root rot using some antagonistic bacteria

Root and collar rot of thuja caused by fusarium oxysporum is one of the important diseases in thuja cultivation. in this research, the effect of eight bacterial strains of bacillus licheniformis, bacillus megaterium, bacillus pumilus, bacillus subtilis, bacillus velezensis, pseudomonas flurescens, pseudomonas koreensi and pseudomonas putida in controlling this disease was investigated in the laboratory. among them, based on the dual culture test and observation of the inhibition zone, b. velezensis and b. subtilis had the highest inhibition with 9.33% and 5.6%, respectively. in the study of the effectiveness of non-simultaneous antifungal volatile compounds, p. flurescens had the highest inhibition with 58.33%. the simultaneous volatile compounds of p. koreensi, p. flurescens, b. pumilus, and b. megaterium completely controlled the disease agent. in the study of the effect of filtered extracellular liquid metabolites on the growth of the pathogen colony, it was observed that with the increase in the concentration of the metabolites, the inhibition percentage of the growth of the pathogen colony by all bacterial strains increases. the best strains against f. oxysporum were b. velezensis, b. subtilis, and b. pumilus strains, which in 25% concentration were 50, 72.27 and 86.67%, respectively, and in 15% concentration b. pumilus strain was 66. 75% and b. velezensis strain with 46.66% inhibition, and at 5% concentration, b. pumilus strain with 44% inhibited the growth of the fungal colony. in the protease production test, all isolates were able to produce protease. only p. fluorescent strain was able to produce a siderophore. in the microscopic studies, all the investigated strains caused morphological changes, fusion of different parts of the filaments, and destruction.