Evaluation of susceptibility to Plum pox virus and European stone fruit yellows phytoplasma in Japanese plum and pluot cultivars

Resistance to PPV and ESFY phytoplasma has been evaluated for Japanese plum ('Aphrodite', 'Black Amber', 'Crimson Glo', 'Santa Rosa') and pluot ('Dapple Supreme', 'Flav Queen', 'Flav Supreme') cultivars. Each cultivar was grafted by chip-budding on GF 305 peach rootstocks and infected with the virulent PPV-Rec or ESFY phytoplasma strain also by chip-budding. After bud break, cultivar evaluation consisted in observing presence or absence of symptoms on leaves, noting the symptom intensity on leaves and on the whole plant. Plants were studied in controlled conditions in a sealed screen-house for three consecutive growth periods. DAS-ELISA and RFLP-PCR analyses were also employed to verify the presence or absence of PPV, respectively ESFY phytoplasma. Results obtained in the context of this very severe biological test against PPV and ESFY phytoplasma confirm the high level of susceptibility of Japanese plum and pluot cultivars.