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Poster

Session: Session 1 Presenting Authors at Posters (Odds)

P-285 - Genomic surveillance of epiphytic Pseudomonas syringae identifies highly virulent strains from phylogroup 2d widespread in UK orchards

Monday, July 14, 2025
13:30 - 15:15  
Location: Confex Hall 3
Population Biology, Ecology & Genomics
In perennial crops, a dynamic reservoir of pathogenic bacteria occurs within the plant surface ecosystem. We examined the role of epiphytic strains of Pseudomonas syringae on cultivated cherry trees and nearby woodland plants in the spread of bacterial canker disease of Prunus. Genomic surveillance of Pseudomonas syringae over two years and in four regions of the UK revealed the presence of diverse phylogroups (PGs) of the species on symptomless leaves. A similar range of PGs was recovered from the two environments; however, the frequency of recovery of PGs was very different, with PG2d strains predominant in orchards and PG2b and PG13a in woodlands. Distinct subclades within PG2d from both environments were highly pathogenic to both cultivated and wild cherry. The pathogens were characterised by the presence of genes encoding the synthesis of the pathotoxin syringolin A and a subset of effector proteins including HopAW1, AvrRpm1 and HopAR1. The leaf surface has emerged as a site for the expansion of reservoirs of pathogenic bacteria which have spread throughout the UK, posing threats to plant health in both agricultural and wild environments. A search for resistance to the emerging, pathogenic PG2d strains should be a priority in the development of new cultivars of cherry. Expansion of the genomic surveillance of the leaf surface environment as described will enable researchers to view management of crop and wild plants on a landscape scale.