Biology, epidemiology, and control of Heterobasidion species worldwide

Heterobasidion annosum sensu lato is a species complex comprising five species widely distributed in coniferous forests of the northern hemisphere, each characterized by distinct host preference. Over 1700 papers have been published on these fungi in the last decades, making them perhaps the most widely studied forest fungi. Heterobasidion species are at different levels on the saprotroph-necrotroph gradient, and the same individual can switch from one mode to the other. This offers a unique opportunity to study how genomic structure, gene expression, and genetic trade-offs may all interact with environmental factors to determine the life mode of the organism. The ability to infect stumps as saprotrophs and to spread to neighboring trees as pathogens has resulted in significant damages to timber production in managed forest. This review focuses on the current knowledge on the biology, ecology, evolution, and management of these species based both on classical and modern studies.