Four auxotrophic strains of the ligninolytio basidiomycetePhanerochaete chrysosporium were obtained by UV mutagenesis. The heterokaryotic mycelium formed by complementation of different auxotrophic isolates was able to fruit and produce basidiospores. From the hasidiospore progeny of the heterokaryons prototrophic strains and strains with a recombined set of parental nutritional requirements were isolated. Genetic recombination hence takes place in fruit bodies produced by the heterokaryotic mycelium.