Ectomycorrhizas were synthesized under axenic conditions between Pinus pinaster (Ait.) Sol. and different mycelial cultures of Hebeloma cylindrosporum Romagnesi. These included a wild dikaryon and four sib-homokaryons (one for each mating type) belonging to the progeny of this fruiting strain.
The homokaryotic mycelia formed typical ectomyeorrhizas showing a morphology and an ultrastructural organization similar to that of ectomyeorrhizas obtained with the parental dikaryon. The ultrastructural localization of acid phosphatase activities was also comparable for homokaryotic and dikaryotic mycorrhizas.
These results demonstrate that the ectomycorrhizal ability is not restricted to the dikaryotic state of fungal life-cycle since homokaryotic mycelia also formed typical and functional ectomyeorrhizas. The formation of normal mycorrhizas by homokaryotic mycelia confirms the usefulness of H. cylindrosporum as a model for genetical studies and improvement of ectomycorrhizal fungi by means of chromosomal genetics.