Monokaryons and dikaryons of Trametes versicolor have similar combative, enzyme and decay ability Jennifer HISCOX*, Christopher HIBBERT, Hilary J. ROGERS, Lynne BODDY Cardiff University, School of Biosciences, Cardiff CF10 3AX, United Kingdom article info Article history: Received 18 December 2009 Revision received 22 February 2010 Accepted 24 February 2010 Available online 10 April 2010 Corresponding editor: Petr Baldrian Keywords: Basidiomycete Dikaryons Interactions Laccase Monokaryons Peroxidase Trametes abstract Heterokaryons (mated mycelia) are commonly used to study basidiomycete ecology, with little known about the relative abilities of homokaryotic (unmated) mycelia. Trametes versicolor is a common wood decay basidiomycete, which fruits prolifically, producing a high proportion of viable basidiospores that germinate readily. The ‘fitness’ of mono- karyotic T. versicolor mycelia was compared to that of dikaryons in terms of extension rate, decay rate, combative ability, and production of ligninolytic enzymes in agar culture and during growth on beech wood blocks. Eight monokaryons, four natural dikaryons and four artificially synthesised dikaryons (created by pairing monokaryotic cultures) were compared, and paired against 11 wood decay species to assess combative ability. There were no significant differences between monokaryons and dikaryons of T. versicolor in any of the characters examined, with as much variation within the karyotic groups as there was between them. When artificial dikaryons and their component monokaryons were considered individually, the dikaryon resembled one of the component mono- karyons rather than being intermediate. This implies that dikaryons behave as functional diploids. ª 2010 Elsevier Ltd and The British Mycological Society. All rights reserved. Introduction The life cycle of a typical wood decay basidiomycete involves two mycelial stages. Spore germination produces a primary, unmated mycelium (monokaryon/homokaryon), which, following hyphal fusion and nuclear exchange with a mating-type compatible conspecific may form a secondary mycelium (dikaryon/heterokaryon). The two haploid gametic types of nuclei are maintained indefinitely during vegetative growth, fusing only for karyogamy and meiosis which yields homokaryotic spores. The heterokaryotic state can also break down through the formation of asexual homokaryotic conidia (Hui et al. 1999 and references within). The hetero- karyotic state is similar to diploidy in that two haploid genomes reside in each cell with full opportunity for genetic complementation, but is crucially different because the two haploid genomes remain separated in different nuclei (Clark & Anderson 2004). The duration of the homokaryotic phase for a mycelium inhabiting woody organic resources is determined by a variety of factors, most important of which are probably the local abundance of the species and its mating-type structure. The homokaryotic phase persists until a compatible conspecific is encountered and there is evidence of an inverse relationship between the number of colonies of a species in the field and the number that are homokaryons (Stenlid 1994). Homo- karyons are often considered short-lived with the hetero- karyotic phase dominating the life cycle, but this is less likely to be the case in areas where mating potential is restricted as the homokaryons would necessarily persist for much longer. For common species, e.g. Trametes versicolor, homokaryons (in this species known to be monokaryons) might be expected to * Corresponding author. E-mail address: evansja7@cf.ac.uk (J. Hiscox). available at www.sciencedirect.com journal homepage: www.elsevier.com/locate/funeco 1754-5048/$ – see front matter ª 2010 Elsevier Ltd and The British Mycological Society. All rights reserved. doi:10.1016/j.funeco.2010.02.003 fungal ecology 3 (2010) 347–356