Biological control of seedling blight of winter wheat caused by Fusarium culmorum and microdochium nivale

Etheridge, Jane Victoria (1997). Biological control of seedling blight of winter wheat caused by Fusarium culmorum and microdochium nivale. PhD thesis The Open University.


The nature of microbial antagonism towards Fusarium culmorum and Microdochium nivale, the primary pathogens implicated in Fusarium seedling blight of wheat, was assessed in laboratory, controlled environment chamber and semi-field experiments. Dual culture experiments, using five different agar media, suggested that three Trichoderma species, Gliocladium roseum, G. catenulatum, Idriella bolleyi and a Finnish fungal isolate, J76, were the most effective of the 30 microorganisms tested in inhibiting mycelial growth of F. culmorum and/or Mnivale. Seedling tests showed that isolates of Gliocladium roseum, G. catenulatum and J76 were the most promising fungi in reducing Fusarium seedling blight on wheat plants. Isolates of these three fungi significantly reduced pre-emergence and post-emergence seedling death and disease severity, measured as the degree of stem base browning.

In vitro, Groseum and G. catenulatum culture filtrates were highly inhibitory to mycelial growth of F. culmorum and Mnivale and also reduced germination of pathogen spores by approximately 9 0%. Culture filtrates of J76 partially inhibited F. culmorum and M. nivale spore germination but had no effect on mycelial growth. Thin layer chromatography (TLC) of a G. roseum culture extract showed nine UV-visible bands of which four displayed antibiotic activity towards F. culmorum. A G. catenulatum culture filtrate produced six UV-visible bands of which two significantly inhibited F. culmorumm ycelial growth. Volatile antibiotics inhibitory towards M. nivale in vitro were produced by isolates of G. roseum, G. catenulatum and J76.

A scanning electron microscope (SEM) study showed that isolates of G. roseum, G.c atenulatum and J76 were necrotrophicm ycoparasites of F. culmorum and M. nivale, killing host cells by direct hyphal contact and causing localised disintegration of the host, probably by enzymatic attack.

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