First report of <i>Neofusicoccum parvum</i> causing canker and dieback on <i>Alnus glutinosa</i> in Portugal

In March 2022, sunken cankers were observed on the stem and branches of young mature Alnus glutinosa trees in central Portugal (Canelas, 40°42’17’’N; 8°33’59’’W). Cankers characterised by necrotic lesions outer inner bark that progressively girdled circumference causing extensive canopy dieback (Figure 1). The incidence disease was estimated at 70% (linear plot 50 m long). To isolate causal agent, 20 samples including twigs, stems collected from seven diseased chosen random along transect. Isolations performed ten chips (5 mm2) xylem tissues cut aseptically margin transferred onto Petri dishes containing potato dextrose agar (PDA). yielded twenty fungal colonies showing a greyish-white aerial mycelium typical Botryosphaeriaceae species. Based colony appearance morphology conidia (hyaline, fusiform, aseptate thin-walled) produced after 15 days sterile Fraxinus ornus twigs PDA 25°C, isolates identified as Neofusicoccum parvum 2). identity confirmed sequencing internal transcribed spacer region two representative isolates, using universal primers ITS1 ITS4. DNA extraction, PCR amplification according to Linaldeddu et al. (2020). A BLASTn search showed 100% with sequence AY236943 ex-type cultures N. (CMW9081). ITS (CBP109) deposited GenBank (Accession No. OQ547268). Pathogenicity tests inoculating an plug (3 mm diameter) active (isolate CBP109) growing wounded two-year-old common alder seedlings methodology reported Ten inoculated fungus ten, used controls, plug. Seedlings kept controlled conditions 21°C watered regularly for 30 days. At end experimental period, all similar those field; six out also wilting symptoms 3). Average lesion size 38 ±14 (mean ±SD). Control plants remained asymptomatic. successfully re-isolated seedlings, thus fulfilling Koch's postulates. This study represents first report affecting Europe. is plurivorous pathogen about 300 plant hosts (Phillips al., 2013; Batista 2021). has been both forest urban environments its pathogenicity different such pine oak (Lopes 2016; 2020). occurrence this invasive species declining recent discovery several Phytophthora same sites (Bregant 2023), could explain rapid devastation ecosystems recently Portugal. research financially supported Land Environment Resources Health (L.E.R.H.) doctoral course (University Padova) project F4F—Forest For Future (CENTRO-08-5864-FSE-000031) Programa Operacional Regional do Centro (Centro 2020), 2020 Fundo Social Europeu. Thanks are due Portuguese Foundation Science Technology (FCT/MCTES) financial support CESAM (UIDP/50017/2020 + UIDB/50017/2020 LA/P/0094/2020) PhD grants Sandra Hilário (SFRH/BD/137394/2018) Eduardo (PD/BD/135535/2018).