Isolation, Characterization, and Avenacin Sensitivity of a Diverse Collection of Cereal-Root-Colonizing Fungi

A total of 161 fungal isolates were obtained from the surface-sterilized roots of field-grown oat and wheat plants in order to investigate the nature of the root-colonizing fungi supported by these two cereals. Fungi were initially grouped according to their colony morphologies and then were further characterized by ribosomal DNA sequence analysis. The collection contained a wide range of ascomycetes and also some basidiomycete fungi. The fungi were subsequently assessed for their abilities to tolerate and degrade the antifungal oat root saponin, avenacin A-1. Nearly all the fungi obtained from oat roots were avenacin A-1 resistant, while both avenacin-sensitive and avenacin-resistant fungi were isolated from the roots of the non-saponin-producing cereal, wheat. The majority of the avenacin-resistant fungi were able to degrade avenacin A-1. These experiments suggest that avenacin A-1 is likely to influence the development of fungal communities within (and possibly also around) oat roots.