The aims of this study were to develop new bioformulations using Trichoderma harzianum, Trichoderma
asperellum, and Talaromyces flavus and some organic and inorganic carriers and evaluate their effects
against Rhizoctonia solani, the fungal causal agent of sugar beet seedling damping-off disease. Selected
fungal isolates were first re-cultured and maintained on potato dextrose agar (PDA) culture medium.
Antagonistic effects of eight isolates of the above-mentioned antagonistic fungi were then evaluated
against R. solani, through volatile metabolites and non-volatile metabolites production mechanisms
under laboratory conditions. In volatile and non-volatile metabolite experiments, five and seven isolates
caused significant reduction in R. solani growth respectively. Based on the results of laboratory experiments,
the most effective antagonistic isolates (one isolate from each species) were selected for development
of nine bioformulations using peat, rice bran and talc as carriers. The effectiveness of developed
bioformulations was then evaluated in controlling sugar beet damping-off disease in a greenhouse
experiment where sugar beet seeds were coated with bioformulations and were sown in pasteurized
field soil pre-inoculated with R. solani. Results of the greenhouse experiment 60 days after sowing
showed that all bioformulations increased the number of healthy seedlings significantly (compared to
the untreated control) with different rates. According to the results, the most effective bioformulation
was Talc-T. harzianum followed by Peat-T. flavus, Talc-T. flavus and Rice bran-T. harzianum. In general, in
both laboratory and greenhouse experiments, T. flavus was the most effective fungal antagonist followed
by T. harzianum and T. asperellum. Based on the results of this study it is concluded that Trichoderma and
Talaromyces employing different mechanisms might be potential biocontrol agents for controlling
R. solani-induced sugar beet damping-off disease.