Mechanism of brown-rot decay: Paradigm or paradox

Interest in understanding how brown-rot fungi degrade wood has received increasing attention in recent years because of a need to identify novel targets that can be inhibited for the next generation of antifungal wood preservatives. Brown-rot fungi are unique in that they can degrade holocellulose (cellulose and hemicellulose) in wood without first removing the lignin. Furthermore, they degrade holocellulose in an unusual manner, causing a rapid decrease in degree of polymerization at low weight loss. Despite increased research effort, the mechanism of brown-rot decay remains unclear. Furthermore, this research has not pointed to biochemical targets for inhibition and development of new wood preservatives. In reviewing the brown-rot literature, it became apparent that many beliefs about brown-rot decomposition of wood are based more on tradition or conjecture than on facts. In some cases, these misconceptions have become near dogma. They cloud our understanding of brown-rot decay and as a result may contribute to a misdirection of research efforts. The purpose of this paper is to attempt to identify and clarify some of these misconceptions.