Production of polyphenol oxidases by ectomycorrhizal fungi with special reference to Lactarius spp.

An investigation of production of polyphenol oxidase by 104 isolates of 67 species of fungi was combined with tests of their ability to form ectomycorrhizas in axenic culture. Most mycorrhizal isolates produced little or no polyphenol oxidase. However, 7 out of 8 Lactarius species produced these enzymes as vigorously as the saprophytic species tested and were insensitive to the quinones formed. These isolates were also presumed to produce cell wall-degrading enzymes since, in contrast to most other ectomycorrhizal fungi, intracellular penetration was a common feature of their mycorrhizas of birch. The possibility that Lactarius spp. are unspecialized, possibly facultative, ectomycorrhizal fungi is discussed.