LAUSR

A total of twenty-five isolates of species Phytophthora cactorum, P. citrophthora, Pythium dissotocum complex, Py. aphanidermatum, Globisporangium heterothallicum, G. ultimum, Phytopythium vexans, Phy. mercuriale and Phy. litorale, isolated from strawberry plants grown in the Czech Republic, were tested to compare their pathogenicity to this host. The tests were performed using the detached leaves technique on five strawberry cultivars—Elsanta, Karmen, Sonata, Honeoye, and Rumba. Both the size and frequency of lesions formed on the strawberry leaflets were evaluated; only weak or no correlation between the size and frequency of developed lesions was discovered. The variability in the level of these correlations between combinations of pathogen isolate and strawberry cultivar corresponded to the existence of two independent resistance components one of them being related to the penetration and the other one to the post-penetration phase of the infection. All tested isolates were verified as virulent, although their virulence against different strawberry cultivars was rather variable; isolates of Phytophthora cactorum performed high variability of the virulence as well. Isolates of Phytophthora citrophthora, Globisporangium ultimum and Phytopythium litorale were evaluated as a most virulent. In general, the most sensitive strawberry cultivar was Elsanta, while the most resistant was Karmen.