Occurrence of Truncatella angustata causing canker and branch dieback of European hazelnut in the Maule region, Chile

Authors: NUNEZ, FERNANDA - University Of Talca; GONZALEZ, PAULINA - University Of Talca; LOLAS, MAURICIO - University Of Talca; MUNOZ, CRISTIAN - University Of Talca; PACHECO, CLAUDIA - University Of Talca; MUBEEN, IQRA - University Of Talca; RODRIGUEZ, PABLO - University Of Talca; FERRADA, ENRIQUE - Austral University Of Chile; Keith, Lisa; DIAZ, GONZALO - University Of Talca

Submitted to: Plant Disease
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/27/2026
Publication Date: 4/7/2026
Citation: Nunez, F., Gonzalez, P., Lolas, M., Munoz, C., Pacheco, C., Mubeen, I., Rodriguez, P., Ferrada, E., Keith, L.M., Diaz, G.A. 2026. Occurrence of Truncatella angustata causing canker and branch dieback of European hazelnut in the Maule region, Chile. Plant Disease. https://doi.org/10.1094/PDIS-01-26-0237-PDN.
DOI: https://doi.org/10.1094/PDIS-01-26-0237-PDN

Interpretive Summary: European hazelnut is grown commercially under Mediterranean-like conditions in the Maule Region in Chile. Symptoms of a general decline, canker and twig death, and branch dieback were recently observed in a commercial orchard containing nine-year-old cv. Tonda Di Giffoni plants. The fungal pathogen causing these symptoms was identified and this work is the first description of Truncatella angustata associated with canker and dieback of hazelnut in Chile.

Technical Abstract: In Chile, the European hazelnut (Corylus avellana L.) is grown commercially on 49,000 ha, with 22,000 ha cultivated in the Maule Region (35°26'S, 71°40'W) under Mediterranean conditions. During a recent survey in a commercial hazelnut orchard in San Clemente, Maule Region containing nine-year-old cv. Tonda Di Giffoni plants, symptoms of canker and dieback were observed (incidence of 5 to 10%). Symptoms included a general decline, canker and twig death, and branch dieback. Cross-sections of diseased twigs and branches revealed firm, necrotic lesions. Diseased branches were disinfected with 96% ethanol, flamed for 15 s, and internal tissue was placed onto acidified potato dextrose agar (APDA) containing 0.1% Igepal and antibiotics (Díaz and Latorre 2014). After a 7-day incubation period at 20 °C, six isolates were obtained and purified by transferring hyphal tips to fresh APDA. After 10 days, colonies developed cottony, opaque white to brown mycelium with black acervuli, and a dark brown pigmentation was observed on the reverse side of Petri dishes. after 10 days on APDA. Conidia were two-celled, brown to dark brown, thick-walled, with hyaline apical and incomplete basal cells. Conidia (n=50) measured (25–) 21 ±1.4 (–18.3) x (8.4–) 6.4 ± 0.6 (–4.8) µm with a length/width ratio of 3.3 and contained prominent septa. Two to four hyaline apical appendages were observed, variable in size and dichotomously branched; the basal appendage was absent. Fungal identification was further confirmed using BLAST analysis of bulk sequenced PCR products of the internal transcribed spacer (ITS1-5.8S-ITS2) region and partial beta-tubulin (Bt) genes for three representative isolates. The gene sequences of T. angustata isolates A3, A40, and A98 were deposited in GenBank (PV687318 to PV687320 for ITS; PV929978 to PV929980 for Bt) and showed 99% similarity compared to sequences of the T. angustata type specimen CPC 21354. Combined phylogenetic analysis using MEGA7 software and the maximum parsimony test clustered the three isolates with T. angustata CPC 21354. Based on morphological and molecular analysis, the fungus was identified as Truncatella angustata (Pers.) S. Hughes (Sutton 1980; Espinosa et al. 2008). For pathogenicity tests, lignified twigs were selected (three isolates; n=45 twigs per pathogen; 20-25 cm long) of hazelnut cv. Tonda Di Giffoni (8 years-old) in San Clemente, Talca. Fresh pruning wounds were inoculated with 40 µL of a 105 conidia/mL suspension. An equal number of twigs (n=15 twigs) were inoculated in a similar manner with sterile water which served as the control. Two months after inoculation, canker lesions at the tip exhibited a length of 15 to 35 mm. No lesions were observed on the control twigs. T. angustata was consistently reisolated (100%) from inoculated twigs and morphologically and molecularly (ITS, Bt) identified, thus fulfilling Koch’s postulates. To the best of our knowledge, this is the first report of T. angustata causing canker and dieback of hazelnut in Chile. This pathogen was previously reported to cause twig dieback of blueberry in Chile (Espinoza et al. 2018). Our findings suggest that T. angustata is involved in a hazelnut dieback complex along with other Botryosphaeriaceae species trunk pathogens in Chile (Moya-Elizondo et al. 2023; Lolas et al. 2024).