This is the report from a BSPP MSc/MRes Bursary.
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Last year I was very lucky to receive an MSc Bursary from the BSPP. This was put toward the cost of undertaking an MSc in Plant Pathology at Harper Adams University. The taught modules allowed me to expand my knowledge of plant pathology principles, whilst also producing pieces of work specific to forest pathology, my area of interest. This included a detailed case study and integrated management programme for Hymenoscyphus fraxineus, the ash dieback pathogen, and diagnostic reports for five tree pathogens identified in the field. I also greatly benefited from modules focused on building research skills and performing statistical analysis using R.
My masters project was supervised by Sarah Green at Forest Research (FR) and investigated pathogen threats to alternative forestry species and provenances in the UK. The reasoning for this lies in the fact that commercial forestry in the UK is currently reliant on a narrow range of species. This entails significant risk when considering the impact of diseases such as sudden larch death and Dothistroma needle blight, caused by Phytophthora ramorum and Dothistroma septosporum respectively. Epidemics of these pathogens have reduced the range of commercially viable timber species and there is considerable interest in identifying novel species to supplement or replace those currently debilitated. An important aspect of determining suitability is understanding how these species/provenances will fare against both invasive and endemic pathogens. My project attempted to address this question by identifying the key pathogen threats to a range of species and provenances being trialled by FR.
This was achieved by completing three main project components: analysis of the FR Tree Health Diagnostic and Advisory Service (THDAS) database, health assessments at two FR species trials and laboratory identification of pathogens obtained from sample material. The THDAS database contains records detailing tree host, pathogen agent, geographical location and woodland type dating back to the 1980s. Relevant records were obtained for the list of alternative species under assessment, so as to identify any recurrent pathogen trends. Health assessments were conducted at two species/provenance trials: one located at Glentress, Scotland, and a second located at Westonbirt, England. Each trial contained one to three provenances of 14 species, arranged in 49-tree plots within three replicated blocks. Thirteen trees were surveyed from each plot, with percentage scores assigned for a range of health variables, including foliage discolouration, foliage dieback and shoot mortality. In clear cases of pathogen infestation, shoot samples were collected for laboratory identification. Isolations were performed by plating shoot material from lesion margins onto malt extract agar. Molecular identification was performed by sequencing DNA samples obtained from shoot material and fungal cultures, with sequence-matching performed using BLAST.
The THDAS database analysis clearly identified Atlas cedar (Cedrus atlantica) as a host species of concern, with 184 reported instances of infection by Sirococcus tsugae. This aligned with observation of numerous symptomatic trees at Glentress and subsequent molecular identification of the pathogen. Atlas cedar has been highlighted for potential use on drier site types in eastern and southern Britain – determining the extent to which disease pressure from S. tsugae may limit the viability of this species would therefore be of value. Analysis of the tree health variables revealed marked differences between provenances of Scots pine (Pinus sylvestris), with Scottish provenances faring significantly better than Polish and Spanish provenances in terms of foliage dieback and shoot mortality. The Weymouth pine (Pinus strobus) fared significantly better than many of the pine species, perhaps suggesting suitability as an alternative species to mitigate the impact of Dothistroma needle blight. However, this potential must be taken alongside the risk posed by Cronartium ribicola, causal agent of white pine blister rust, a disease which has severely debilitated the Weymouth pine in North America. With regard to molecular analysis of sample material, the two most frequently identified fungal species were Gremmeniella abietina and Coniothyrium lignorum. Gremmeniella abietina is the causal agent of Brunchorstia dieback, a shoot disease of pines, and, alongside D. septosporum, will therefore have contributed significantly to observed damage. With no reported instances of pathogenic activity, C. lignorum is most likely an endophyte.
Whilst these results provide a brief summary of the project’s key findings, a range of pathogen species and varying host responses were identified. This work represents a preliminary investigation of pathogen threats to alternative forestry species/provenances. Greater insight could be gained by expanding the geographical range of assessed species trials and by conducting inoculation experiments to better understand host responses to the key pathogen agents identified.
Harper Adams University
Image 2: Symptoms of Sirococcus tsugae infection on a French provenance of Cedrus atlantica at Glentress.
Image 3: View of Glentress species/provenance trial.