2.1. Bacterial isolates and culture conditions

The 36 E. amylovora isolates used in this study were isolated between 2010 and 2017 from fruits, trunk exudates, and branches from symptomatic apple and pear orchards trees, located at the main production region of pome fruits in Portugal (Table 1, S1 Fig), and were cultured at 28°C on King’s B medium (20 g of Peptone protease number 3; 10 mL of glycerol; 1.5 g of K₂HPO₄; 1.5 g of MgSO₄.7H₂O; 18 g of agar; distilled water up to 1L) [58]. Bacterial cultures were stored in King’s B medium at -80°C in 30% glycerol. In the present study, E. amylovora isolates and the type strain LMG 2024 (used as a positive control for polymerase chain reaction amplification (PCR), dot blot hybridization and immature pear assay), were recovered and cultured on King’s B medium at 28°C.

* These isolates have been isolated in the West region of Portugal, which includes the municipalities Alcobaça, Caldas da Rainha, Alenquer and Cadaval (S1 Fig).