THE SAPROTROPHIC WOOD-DEGRADING ABILITIES OF HETEROBASIDIUM-ANNOSUM INTERSTERILITY GROUP-P AND GROUP-S

The saprotrophic wood-degrading abilities of strains hom the interster ility groups S and P of the necrotrophic root and white rot fungus Het erobasidium annosum were tested using a conventional soil jar method a nd small wood blocks of Pinus sylvestris, Picea abies and Betula verru cosa. Weight loss in dry matter of wood blocks was compared with the a bility of the same strains to secrete the phenol oxidase laccase under liquid and solid-state culture conditions. Results showed the much gr eater ability of H. annosum P strains to degrade wood, with weight los ses comparable to those reported for other white rot fungi cultivated under similar conditions. In contrast; the S isolates except Br228 and Fr154 degraded the wood blocks poorly with a maximum weight loss of c a 12% recorded after 5 mo incubation. Light and scanning electron micr oscopy showed hyphal colonization and decay to be typical for white ro t, with both simultaneous attack by cell wall thinning and preferentia l lignin degradation recorded for P strains. Results for wood block de gradation correlated well with the ability of the intersterility group s to produce laccase in liquid culture and solid-state culture conditi ons, with P strains producing ca 5-6 times more laccase than S strains . Results indicate that great differences exist between H. annosum int ersterility P and S groups ability to cause wood decay, but that P str ains have a significantly greater competitive saprotrophic wood-degrad ing ability than previously realized.