Pathogenicity, morphology and genetic variation of Phytophthara cactorum from strawberry, apple, rhododendron, and silver birch

The analysis of random amplified microsatellite (RAMS) markers of Phytophthora cactorum from strawberry showed that leather rot of strawberry fruits and crown rot are not caused by genetically different strains of this species. UPGMA-analysis showed that the populations of P. cactorum on strawberry differ between North America and Europe and that no clear genetic separation between isolates from different plants can be made among these populations. Slight morphological variation exists in the diameters of oogonia and oospores among the isolates but is insufficient for the identification of genetic groups or host specificity of P, cactorum isolates. Pathogenicity experiments proved that strains show a tendency towards host specialization.