SOFT-ROT AND MULTIPLE T-BRANCHING BY THE BASIDIOMYCETE INONOTUS-HISPIDUS IN ASH AND LONDON PLANE

Wood degradation by the white-rot basidiomycete Inonotus hispidus was studied in ash (Fraxinus excelsior) and London plane (Platanus x hispa nica). After 6 or 12 wk incubation of inoculated wood blocks the loss of dry weight was greater in plane than in ash, corresponding with a m ore intense visible degradation of the secondary walls in the lignifie d axial cells. Atypically for a white-rot, degraded cell walls contain ed internal cavities. The cells thus affected were the late-wood fibre s in ash and the fibre tracheids in plane. The structure of the caviti es and the formation of multiple T-branches by the associated hyphae w ere typical of a soft-rot normally associated with certain Deuteromyco tina and Ascomycotina. Naturally infected wood from a living plane tre e contained cavities identical to those found in the wood blocks, and also showed typical white-rot degradation where the decay was more adv anced, with dissolution of the middle lamellae and the induction of pr ogressive wall thinning by hyphae in the lumina of axial and ray cells . In the inoculated blocks, only ash showed degradation of ray cells, even after 12 wk incubation. Another form of degradation, observed in the early-wood fibres of the ash blocks, was notch-erosion at the cell wall/lumen interface, typical of both white-rot and some soft-rot fun gi.