Developing durable disease resistance to bacterial canker of cherry

Bacterial canker, caused by Pseudomonas syringae is a major disease of cherry, for which there is no effective control. This project aims to use bioinformatic and experimental approaches to understand the host adaptation and pathogenicity of P. syringae and elucidate how Prunus resists infection, with the intention of using the outcomes to deliver impact to industry via new markers for resistance. This will be addressed by four questions. First, how is host specificity determined by effector content; do conserved effectors, over-represented in convergently evolved Pseudomonas clades, play an essential role in adaptation in Prunus? Second, what is the basis of niche survival and persistence of P. syringae on cherry; do different complements of host specificity factors determine survivability? Thirdly, which effectors control known resistance responses in cherry? Fourthly, what is the genetic architecture of resistance to P. syringae in cherry? From bioinformatics analysis, the role of specific conserved effectors across convergently evolved P. syringae clades will be characterised and their role in pathogenicity determined though creation of polymutants. Using transposon tagging techniques coupled with competition experiments (InSeq), functional characterisation of factors controlling niche specificity will be determined. Using Pseudomonas as a delivery vector for specific effectors, the long established ‘race’ structure of P. syringae pv. morsprunorum will be dissected and loci involved in resistance to both ‘broad spectrum’ and race specific resistance will be identified in collaboration with industry partners. This will allow the identification of molecular markers for resistance that will facilitate the breeding of commercially viable resistant cultivars.

Publications:

Hulin M.T., Armitage, A.D., Vicente, J.G., Holub, E.B., Baxter, L., Bates, H.J., Mansfield J.W., Jackson, R.W., Harrison, R.J. 2018. Comparative genomics of Pseudomonas syringae reveals convergent gene gain and loss associated with specialisation onto cherry (Prunus avium). bioRxiv. DOI: 10.1101/244715

Hulin M.T., Mansfield J.W., Brain, P., Xu, X., Jackson R.W. and Harrison R.J. Characterisation of the pathogenicity of strains of Pseudomonas syringae towards cherry and plum. Plant Pathology. Accepted article online. DOI: 10.1111/ppa.12834

Principal Investigator: Richard Harrison

Researchers: Michelle Hulin, Bo Li, Kieran Housley

Funder: BBSRC

Duration: 4 years (2017-2021)

Partners: Berry Gardens, AHDB and GreenYard Fresh (Commercial). University of the West of England, University of Reading (academic)

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The perennial lifecycle of bacterial canker disease on Prunus. Diagram shows the different plant tissues that are inhabited by the bacteria throughout the year and mode of transmission.

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Cherry pathogenicity has evolved multiple times in Pseudomonas syringae. Multi-locus phylogeny based on 1035 genes which represent the core genome of P. syringae. Strains from cherry and plum are highlighted in pink and blue respectively. Strains pathogenic to cherry are labelled with red circles. Phylogroups are also labelled in green. Percentage bootstrap support values below 99% are shown for each node. The scale is nucleotide substitutions per site.

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