First report of hazelnut kernel rot caused by <i>Stemphylium vesicarium</i> in Italy

Hazelnut (Corylus avellana) is one of the most cultivated nut crops worldwide, with Turkey (665,000 tonnes) and Italy (140,560 representing leading countries in global production (Król & Gantner, 2020). During summer 2022, a survey was done to identify fungal species associated hazelnut kernel rot five commercial orchards Latium region Italy. A newly recorded isolated from diseased nuts using standard techniques 17.91% 380 samples analysed. Pure cultures were white light grey reverse colony colour being deep brown or circular alternate band growth pattern (Fig. 1). Multicellular, brown-pigmented, subspherical, verrucose conidia developed after eight days on V8 medium, measuring 13.6-34.0 μm × 10.2-20.4 2). Ascomata forming culture contained hyaline, bitunicate, clavate asci four ascospores that medium brown, ellipsoidal, transverse several longitudinal septa, 10.2-13.6 23.8-37.4 Morphological characteristics corresponded those Stemphylium spp. (Simmons, 1969). Genomic DNA three representative isolates (V1, V2 V3) extracted 100 mg fresh mycelium following NucleoSpin® Plant II kit manufacturer's protocol for fungi (Macherey-Nagel, Germany). The internal transcribed spacer (ITS), glyceraldehyde-3-phosphate dehydrogenase (GAPDH) calmodulin (CMD) gene regions amplified sequenced primers ITS1/ITS4 (White et al., 1990), gpd1/gpd2 Cal228f/Cal2rd (Woudenberg 2017), respectively. An nBLAST analysis sequences (GenBank Accession Nos. OQ605535-OQ605537 ITS; OQ724528-OQ724530 GAPDH, OQ724531-OQ724533 CMD) revealed 100% identity deposited S. vesicarium. Pathogenicity tests pure isolate V1. Inoculations mesocarp performed two techniques: (i) inoculation potato dextrose agar (PDA) plugs 5 mm diameter seven-day-old PDA colonies, (ii) 20 μl conidial suspension (105 conidia/ml). Control fruits treated clean sterile water, Fruits placed moist chamber at 25°C 10 days. kernels inoculated both showed same severe necrosis rotting seven ten inoculation, whereas controls remained non-symptomatic 3). To fulfil Koch's postulates, vesicarium reisolated symptomatic confirmed morphologically molecularly. Recently, reported causing leaf spot spinach (Gilardi 2022). pathogen also as causal agent pear Europe (Llorente Montesinos, 2006). However, best our knowledge, this first report disease globally. These findings suggest could severely affect research carried out frame “Econocciola” project.