GENETIC-VARIATION AND HOST-SPECIFICITY OF PHYTOPHTHORA-CACTORUM ISOLATED IN EUROPE

Analysis of Phylophthora cactorum using Random Amplified Microsatellit es (RAMS) revealed considerable variation among isolates, most of whic h correlated with the original host plants. The lack of variation amon g isolates originating from strawberry suggests that crown rot of stra wberry is caused by a single clone within the geographical area studie d. It was also shown that P. cactorum isolates form a unique group dif ferent from other Phytophthora spp. from Group I. P. cactorum isolates from necrotic stem lesions on Betula pendula seedlings or Fragaria x ananassa plants suffering from crown rot were highly pathogenic to the ir original host plants. P. cactorum isolates from strawberry inoculat ed via wounds also caused necrotic lesions on B. pendula. On the other hand isolates from B. pendula did not cause disease symptoms on straw berry plants. On Alnus glutinosa the percentage of successful inoculat ions with a birch isolate was 40.