Impact of tannins from bioactive plants on the growth of the biocontrol fungus Duddingtonia flagrans

Nematode infections in the ruminant livestock systems cause significant loss each year in both animal health and production. There are several control methods to combat nematodes. The most common are the anthelmintics, but there are several alternatives such as bioactive plants, nematophagous fungi, vaccination, and selective breeding. The use of alternatives such as biocontrol fungi and bioactive plants, alone and in combination have become more attractive prospects with increasing anthelmintic resistance and a growing organic livestock sector. The interaction between these alternative methods is not well understood. This study uses radial growth plates of the biocontrol fungus Duddingtonia flagrans in the presence of various bioactive forages at both 25°C and 15°C. Plant secondary metabolites present in bioactive plants specifically tannins, were found to be inhibitory towards D. flagrans and this inhibition was found to be temperature dependent. This is the first quantitative evidence of an interaction between D. flagrans and tannins and the first indication of the potential presence of a tanniferase enzyme within a nematophagous fungi. Further work should be conducted in the natural fecal environment and with other biocontrol fungal candidates.