First report of the fungus <i>Gnomoniopsis smithogilvyi</i> causing cankers on sweet chestnut ( <i>Castanea sativa</i> ) in Ireland

In autumn 2020 cankers and branch dieback (Figure 1) were found in a five-year-old gene bank plantation of Castanea sativa Wicklow, Ireland. The planting material had been imported as grafted saplings from the United Kingdom. Isolations made by surface sterilising outer bark near with 70% ethanol. Pieces (5 × 5 5mm) woody removed soaked 2% NaOCl for one minute, followed two one-minute distilled water washes. After dabbing dry using paper towels pieces placed aseptically onto malt extract agar (MEA; Difco™) incubated at 21°C dark three weeks. several days, hyphal tips taken fungal colonies transferred potato dextrose (PDA; DifcoTM). DNA was extracted mycelium seven-day old cultures ITS region sequenced primers ITS5 ITS4. Gnomoniopsis smithogilvyi (syn. G. castaneae) 2) detected. Microscopic observations agreed published descriptions Shuttleworth et al. (2012) Visentin (2012). sequences deposited GenBank under accession numbers OM683278 OM683279. Sixty three-year-old C. inoculated either isolates, or control sterile PDA plug (Table 1). ethanol, stem wound 6 mm cork borer, 10 cm above soil level. A mycelial three-week-old isolate wound. This then covered moist sterilised cotton wool, wrapped plastic film, aluminium foil. Control plants plugs. Treatments randomised grown outside, between mid-August to mid-November (mean temperature 14.9°C; mean relative humidity 85.5%). six weeks necrotic lesions 3; Table observed on all which re-isolated lesions. caused girdling numerous 4). identity reisolated confirmed morphological assessment sequencing, fulfilling Koch's postulates. All be asymptomatic, no isolated these (0/8 attempted re-isolations). causes hybrids Spain, five European countries (Shuttleworth al., 2016; Lewis 2017; Lione 2019). It also chestnut rot Australia, France, Italy, New Zealand, Portugal Switzerland (Visentin 2012; Coelho & Gouveia, 2021). is first report causing Follow up surveys tests are planned fully understand distribution