Sexuality and mating types of Ganoderma philippii, Ganoderma mastoporum and Ganoderma australe, three basidiomycete fungi with contrasting ecological roles in south-east Asian pulpwood plantations

Species of Ganoderma, particularly G. philippii, G. australe and G. mastoporum, are commonly found in Indonesian Acacia mangium plantations. Ganoderma philippii is a root rot pathogen while the other two species are secondary root invaders and wood rotters. Management of G. philippii can be supported by knowledge of its gene flow, genetic diversity and population dynamics. This investigation was undertaken to determine the sexuality and mating systems of G. philippii and co-occurring Ganoderma species, observing the somatic interactions between monokaryotic and dikaryotic mycelia and noting any incompatibility mechanisms. In all three species monokaryons were self-sterile. By examining the contact-zone hyphae, it was determined that in all three species, full sexually compatible matings occurred in 26-33% of the crossings. Two mating type loci were identified, as is the case for a wide range of Basidiomycetes. Dikaryons generated from monokaryotic isolates showed morphological changes as cultures aged. The results of this study indicate that outcrossing is favoured in all three species, G. australe, G. philippii and G. mastoporum, therefore promoting adaptation to new hosts and environments.