Genetic variation between Phytophthora cactorum isolates differing in their ability to cause crown rot in strawberry

Analysis of 44 isolates of Phytophthora cactorum, isolated from strawberry and other hosts, by AFLP showed that the crown rot pathotype is different from leather rot isolates and from P. cactorum isolated from other hosts. 16 of 23 crown rot isolates. including isolates front Europe, Japan, Australia, and New Zealand, were identical in an analysis based oil 96 polymorphic bands front seven printer combinations. Leather rot isolates of strawberry could not be distinguished from isolates front other hosts. The pathogenicity test of all 44 isolates oil strawberry plants mostly gave unambiguous results, except for three American isolates, which seemed to have reduced aggressiveness compared to the crown rot isolates. These isolates also differed in the AFLP analysis. Comparing information on the origin of the isolates with results from the pathogenicity test, showed that isolates from strawberry fruits or petioles could be either leather rot or crown rot pathotypes. None of the isolates from hosts other than strawberry caused crown rot symptoms in strawberry.