The cell wall of Fomes annosus (Heterobasidion annosum) as a target for biochemical control: 2. The influence of inhibitors of cell wall synthesis
1982
Flemming, Sabine | Cwielong, P. | Hüttermann, A.
Polyoxin‐D is a competitive inhibitor of chitin‐synthetase of Fomes annosus. Addition of Polyoxins to the culture medium of F. annosus resulted into reversible inhibition of growth at very low concentrations, without actually killing the fungus. SUMMARY: Polyoxin‐D inhibits at very low concentrations (20 μm) already the activity of chitin‐synthetase of Fomes annosus. The mechanism of this inhibition was determined as being competitive inhibition. The inhibitor competes with the natural substrate (Uridinediphospho‐N‐acetyl‐glucosamine) for the substrate binding site of the enzyme. The ratio between the inhibitor constant K*** and the Michaelis constant Kₘof the natural substrate is about 100. This value is a very good basis for long term control of the fungus in vivo. The addition of the technical grade Polyoxin‐mixture to the culture medium of Fomes annosus resulted into inhibition of growth at the same low concentrations of the drug, too. Compared to the toxic effects of phenols on the fungus (Haars et al. 1981), Polyoxins are 100 times more efficient. The inhibition, however, is reversible, no killing of the fungus was observed at concentrations resulting into complete inhibition of growth. The addition of L‐threonine to the culture medium had no synergistic effect on the Polyoxin action. The insecticide Dimilin which has been reported to inhibit chitin synthesis in insects (Deul et al. 1978) did not have any inhibitory effect on chitin synthetase of Fomes annosus in vitro or on growth of the fungus in vivo.
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