Mutants of resistant to fungicides and antibiotics were used for inves
tigations of the hyphae and nuclei migrations in vegetative compatible
and incompatible combinations on Phytophthora infestans strains. The
all types of interactions are defined by two properties of the interac
ted strains: frequency of hyphal fusions and intensity of incompatible
reaction. The only heterokaryon between vegetatively incompatible str
ains was obtained.