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 <i>Ganoderma</i>, particularly <i>G. philippii, G. australe</i> and <i>G. mastoporum</i>, are commonly found in Indonesian <i>Acacia mangium</i> plantations. <i>Ganoderma philippii</i> is a root rot pathogen while the other two species are secondary root invaders and wood rotters. Management of <i>G. philippii</i> 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 <i>G. philippii</i> and co-occurring <i>Ganoderma</i> 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, <i>G. australe, G. philippii</i> and <i>G. mastoporum</i>, therefore promoting adaptation to new hosts and environments.