Characterising broad-acting resistance to bacterial canker of cherry and elucidating tissue-specific mechanisms of immunity

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Bacterial canker is a major disease of cherry caused by various Pseudomonas syringae pathogens that occupy different tissues throughout the season. Resistance breeding could play a large role in limiting this disease. Our research has shown that broad-acting partial resistance towards all pathogens is exhibited by some cherry cultivars. This resistance is likely to be quantitative, involving a range of traits. In contrast, wild cherry accessions exhibit strong resistance that may be simply inherited and involve one or a few major genes. This PhD project will focus on characterising the genetic basis of resistance by genotyping and phenotyping wild and sweet cherry populations propagated at East Malling, with the aim to identify novel sources of resistance to canker. This would lead to the development of molecular markers for use in breeding. In addition, the student will begin to study the biological basis of resistance responses in different host tissues. Ongoing work on bacterial canker has shown that different tissues vary in their susceptibility. Field resistance is not replicated fully in leaf and fruit tests. The student will optimise assays to understand immune responses e.g. measurement of reactive oxygen species and study immune gene expression. They will use microscopy of fluorescently tagged strains to follow infection and bacterial mutants to dissect the immune responses occurring.