The purpose of this study was to
survey the growth inhibition with volatile antibiosis and killing of Pythium
irregulare by Trichoderma species of various origin under heavy metal stress.
Fourteen strains of T. harzianum, 10 strains of T. virens, and 14 strains of T.
viride were tested in dual culture with the pathogen on heavy metal poisoned
media. Minimum inhibitory concentrations (MIC) for mycelial growth, antibiosis
and Pythium-killing were determined. Although the decreasing order of toxicity
(Cd≯Ni≯Zn) was the same for the growth of Pythium and the antagonists,
the pathogen tolerated 2-4 times higher doses of toxic metals
than Trichoderma strains did. The antagonistic activities proved to be more
sensitive, they were blocked by 0.16-0.67
mM Cd, 0.16-1.25 Ni or Zn. Pythium-killing was observed at higher doses
of Ni than that of Cd or Zn, which were similar toxic to the both investigated
activities. The history of long-term heavy metal exposure of some investigated
Trichoderma strains did not increase the tolerance of mycelial growth, but the
antagonistic activities were more sensitive in those strains that had
originated from not polluted arable soils.