The aim of this master’s thesis was to evaluate the antagonistic potential of selected
Trichoderma spp. isolates against selected soil-borne phytopathogenic fungi Agroathelia
rolfsii, Sclerotinia sclerotiorum and Sclerotium cepivorum at 15 and 25 °C. The isolates
T. atroviride and T. afroharzianum from Tricho Immun, Vintec, and local isolates KIS
1872 and KIS 2885 from mycological collections of Agricultural Institute of Slovenia,
were tested using a dual culture assay. Mycelial growth was monitored for ten days,
colony area was measured, growth inhibition was calculated, and interactions between
antagonists and pathogens were visually assessed. The results showed that all
Trichoderma spp. isolates grew faster at 25 °C than at 15 °C; at 25 °C all isolates overgrew
the agar plates by the fourth day after inoculation, whereas at 15 °C the isolate T.
afroharzianum from the Tricho Immun product showed particularly poor growth. In most
treatments, the isolates significantly reduced pathogen growth compared to the controls.
At 25 °C, inhibition levels were relatively similar among isolates, while at 15 °C the
isolate T. atroviride from Vintec was the most effective and isolate T. afroharzianum
from Tricho Immun the least effective antagonist. The highest inhibition was observed
against S. sclerotiorum, especially at 25 °C. Sclerotia formation was also monitored as an
indicator of the effect of antagonists on pathogen development. A. rolfsii formed sclerotia
only at 25 °C, with the highest number on control plates, while S. sclerotiorum formed
sclerotia only on the control plate at 25 °C. In S. cepivorum, sclerotia were present in all
treatments. The results confirm that the antagonistic activity of Trichoderma spp. isolates
depends on temperature, pathogen species and the individual isolate.
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