The aim of this study was to test the ability of dead wood colonization of Heterobasidion annosum isolates with known aggressiveness to the Scots pine seedlings. The experiment was established in Scots pine stand localized in the Człopa Forest District. Roots of six-month-old stumps were inoculated with mycelium of 19 genotypes of H. annosum Genotypes colonized wood of Scots pine roots on distance from 8.10 cm to 43.27 cm. The genotypes that colonized wood on a shortest distance and the most extensively differed significantly from others. The analysis of the ability of wood colonization by mycelium of genotypes in relations to its origin showed that genotypes collected from stumps overgrew the roots slightly stronger (about 14.5%) than those collected from trees, but differences were not significant. There were no differences between genotypes isolated from pines and beaches, either. Population of H. annosum differed in genotypes features conditioning the rate of its development in the environment and disease dynamics. Differentiation of these features of pathogen populations caused an unequal infection and disease development rate in stands. It seems that the most aggressive isolates colonize the stand fastest through root system.

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