Plant diseases caused by bacteria remain problematic for the global horticultural industry due to a lack of effective control measures (Sundin et al., 2016). The genus Prunus contains over 400 species, a selection of which are grown for top fruit, ornamental use and timber production (Bortiri et al., 2001). Bacterial canker, caused by members of the Pseudomonas syringae species complex, can be a major limiting factor in the cultivation of Prunus spp. (Omrani et al., 2019;Vicente et al., 2004). The disease is primarily characterized by necrosis, gummosis and/ or dieback of woody plant tissues. In addition, the pathogens colonize other plant tissues where they exist epiphytically or invade to cause leaf and fruit spots, and blossom blight. These tissues can act as reservoirs

Summary Many strains of Pseudomonas colonise plant surfaces, including the cherry canker pathogens, Pseudomonas syringae pathovars syringae and morsprunorum. We have examined the genomic diversity of P. syringae in the cherry phyllosphere and focused on the role of prophages in transfer of genes encoding Type 3 secreted effector (T3SE) proteins contributing to the evolution of virulence. Phylogenomic analysis was carried out on epiphytic pseudomonads in the UK orchards. Significant differences in epiphytic populations occurred between regions. Nonpathogenic strains were found to contain reservoirs of T3SE genes. Members of P. syringae phylogroups 4 and 10 were identified for the first time from Prunus. Using bioinformatics, we explored the presence of the gene encoding T3SE HopAR1 within related prophage sequences in diverse P. syringae strains including cherry epiphytes and pathogens. Results indicated that horizontal gene transfer (HGT) of this effector between phylogroups may have involved phage. Prophages containing hopAR1 were demonstrated to excise, circularise and transfer the gene on the leaf surface. The phyllosphere provides a dynamic environment for prophage‐mediated gene exchange and the potential for the emergence of new more virulent pathotypes. Our results suggest that genome‐based epidemiological surveillance of environmental populations will allow the timely application of control measures to prevent damaging diseases.

Fruit quality attributes are influenced by environmental, agronomic and genetic factors; both cultivars and growing conditions can vary substantially between UK production and imported fruit. This study aimed to record and dissect the most relevant fruit quality traits for berries imported into the UK in the winter months. Blackberry, blueberry, raspberry and strawberry fruit were imported from 11 countries into a Kent-based packhouse (UK) or purchased from major retailers between December 2018 and March 2019. Multiple fruit quality components were assessed for relative contribution towards a high “overall assessment” fruit quality score. It was found that strawberry and blackberry overall scores were affected by sweetness perception, whereas blueberry and raspberry organoleptics are more complex, with overall scores influenced by flavor perception. Multiple raspberry and strawberry fruit quality traits were found to be associated with genotypic differences, indicating a promising potential for genetic improvement through breeding. By contrast, the study findings suggest that there is less potential for genetic improvement in blueberry, and that the environment may have a large effect on blueberry fruit quality traits.