Analysis of Phytophthora cactorum using Random Amplified
Microsatellites (RAMS) revealed considerable variation among isolates,
most of which correlated with the original host plants. The lack of variation
among isolates originating from strawberry suggests
that crown rot of strawberry is caused by a single clone within the geographical
area studied. It was also shown that P. cactorum
isolates form a unique group different from other Phytophthora
spp.
from Group I.
P. cactorum isolates from necrotic stem lesions on Betula
pendula seedlings or Fragaria × ananassa plants
suffering from crown rot
were highly pathogenic to their original host plants. P. cactorum
isolates from strawberry inoculated via wounds also caused necrotic
lesions on B. pendula. On the other hand isolates from B.
pendula did not cause disease symptoms on strawberry plants. On Alnus
glutinosa the percentage of successful inoculations with a birch isolate
was 40.