Wood decomposition by Phellinus (Fomes) pini: a scanning electron microscopy study

Abstract

Decomposition of white pine (Pinus monticola Dougl.) and western larch (Larix occidentalis Nutt.) by the white-pocket rot fungus, Phellinus (Fomes) pini (Thore ex Fr.) A. Ames, was investigated using scanning electron microscopy. White tissues surrounded by apparently sound wood characterized the decay. Latewood was first to be colonized and degraded. A selective degradation of lignin was observed. The middle lamella between tracheids was completely decomposed. The primary and secondary cell wall contained a macrofibrillar structure indicating lignin was removed leaving a cellulose framework. Macrofibrils 0.2–0.4 μm were present. In white-pocket regions, ray parenchyma was completely degraded. Sound wood, bordering white-pocket areas, usually consisted of early wood and resin-filled ray parenchyma. Fungal hyphae and bore holes were present in surrounding wood but decay typical of white-pocket rot was not observed. In addition to white-pocket rot, P. pini causes a brownish decay in wood near sporophores and punk knots that is ultrastructurally similar to decay by a white rot fungus. The potential use of white-pocket rot decay as a livestock feed and use of P. pini in a biological pulping process for the production of paper is discussed.