Variability in pathogenicity among Greek isolates of Phytophthora cactorum to four peach rootstocks

Studies on 8 isolates of Phytophthora cactorum recovered from different plants identified the presence of diversity in pathogenicity. All isolates appeared pathogenic to tested peach rootstocks but with variable levels of aggressiveness. The peach and almond isolates were the most aggressive. In contrast, the apple and strawberry isolates were least aggressive. Generally, the aggressiveness of P. cactorum isolates did not differ among peach rootstocks. The weak aggressiveness of isolates of P. cactorum from apple trees and strawberry plant suggests that these isolates are not a serious threat to peach rootstocks. This study also confirms that laboratory techniques, such as the excised-twig assay, correlate well with field evaluations.