Abstract
Phytophthora austrocedri is a recently invasive pathogen causing widespread mortality of the ecologically important native conifer, Juniperus communis, in northern Britain. Observations of disease symptoms at severely infected woodlands revealed the presence of individual, apparently healthy trees in areas of high mortality. This study was undertaken to test the hypothesis that these ‘survivor’ trees have greater resistance to P. austrocedri. Rooted cuttings were obtained from seventeen putatively resistant J. communis clones at two heavily infected natural woodlands. Inoculation of excised stems from three putatively resistant clones with P. austrocedri provided initial data to support the hypothesis of resistance. A larger trial was conducted in which whole J. communis plants representing seventeen putatively resistant clones and a known susceptible clone were inoculated with two isolates of P. austrocedri. This trial revealed variation in resistance, with at least six clones exhibiting a high degree of resistance to the pathogen. One surprising finding given the lack of genetic diversity in UK P. austrocedri isolates was that one of the clones was resistant to one isolate and susceptible to the other, warranting further investigation. The next steps are to ascertain whether this natural resistance in J. communis is heritable and exploitable for population recovery.
This is a preview of subscription content, log in via an institution to check access.
Data availability
All data are published in the manuscript.
References
Bates D, Maechler M, Bolker B, Walker S (2015) Fitting linear mixed-effects models using lme4. J Stat Softw 67:1–48. https://doi.org/10.18637/jss.v067.i01
Donald F, Green S, Searle K, Cunniffe NK, Purse B (2020) Small scale variability in soil moisture drives infection of vulnerable juniper populations by invasive forest pathogen. For Ecol Man 473:118324. https://doi.org/10.1016/j.foreco.2020.118324
Elliott CG, Hendrie MR, Knights BA (1966) The sterol requirement of Phytophthora cactorum. J Gen Microbiol 42:425–435
Green S (2018) Phytophthora austrocedri. CABI Invasive Species Compendium https://www.cabi.org/isc/datasheet/108927
Green S, Elliot M, Armstrong A, Hendry SJ (2015) Phytophthora austrocedrae emerges as a serious threat to juniper (Juniperus communis) in Britain. Plant Path 64:456–466
Greslebin AG, Hansen EM (2010) Pathogenicity of Phytophthora austrocedrae on Austrocedrus chilensis and its relation with mal del ciprés in Patagonia. Plant Pathol 59:604–612
Greslebin AG, Hansen EM, Sutton W (2007) Phytophthora austrocedrae sp. nov., a new species associated with Austrocedrus chilensis mortality in Patagonia (Argentina). Mycol Res 111:308–316
Henricot B, Pérez-Sierra A, Armstrong A, Sharp PM, Green S (2017) Morphological and genetic analyses of the invasive forest pathogen Phytophthora austrocedri reveal two clonal lineages colonised Britain and Argentina from a common ancestral population. Phytopath 107:1532–1540
Hothorn T, Bretz F, Westfall P (2008) Simultaneous Inference in General Parametric Models. Biometrical J 50:346–363
Lenth R (2019) Emmeans: Estimated marginal means, aka least-squares means. Retrieved from https://CRAN.R-project.org/package=emmeans
R Core Team (2018) R: A language and environment for statistical computing. R Foundation for Statistical Computing, Vienna, Austria. Available online at https://www.R-project.org/.
Riddell CE, Dun HF, Elliot M, Armstrong A, Clark M, Forster J, Hedley PE, Green S (2020) Detection and spread of Phytophthora austrocedri within infected Juniperus communis woodland and diversity of co-associated Phytophthoras as revealed by metabarcoding. For Pathol. https://doi.org/10.1111/efp.12602
Thomas P, El-Barghathi M, Polwart A (2007) Biological Flora of the British Isles: Juniperus communis L. J Ecol 95:1404–1440
Wickham H (2016) ggplot2: elegant graphics for data analysis. Springer-Verlag, New York
Acknowledgements
The authors wish to thank Rachael Campbell for assistance with the greenhouse trials and Joan Cottrell for a critical review of the manuscript. The work was undertaken under quarantine licence PH/23/2016 and funded by the Forestry Commission.
Funding
This work was funded by the Forestry Commission.
Author information
Authors and Affiliations
Corresponding author
Ethics declarations
Conflicts of interest/Competing interests
The authors declare no conflict of interest.
Ethics approval
Not applicable.
Consent to participate
Not applicable.
Consent for publication
Not applicable.
Code availability
Not applicable.
Additional information
Publisher’s note
Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.
Rights and permissions
About this article
Cite this article
Green, S., James, E.R., Clark, D. et al. Evidence for natural resistance in Juniperus communis to Phytophthora austrocedri. J Plant Pathol 103, 55–59 (2021). https://doi.org/10.1007/s42161-020-00693-1
Received:
Accepted:
Published:
Issue Date:
DOI: https://doi.org/10.1007/s42161-020-00693-1