Occurrence of Xanthomonas arboricola pv. corylina on hazelnut orchards in Sardinia and Sicily

In the course of field surveys carried out in hazelnut (Corylus avellana) orchards of Sardinia [Barbagia di Belvì (Nuoro)] and Sicily [Nebrodi (Messina) and Etna (Catania)] symptoms resembling those incited by Xanthomonas arboricola pv. corylina Vauterin et al. were observed. Brownish, elliptical, water-soaked necrotic spots were present on fruit husks and, sometimes, twigs showed partial die-back. Tissues from lesion margins were ground in a mortar containing physiological sterile saline. Aliquots (0.1 ml) of serial ten-fold dilutions of the homogenate were plated on Yeast extract-dextrose-calcium carbonate agar and incubated at 25-27°C for three days. The resulting circular, mucoid, yellowish colonies were subjected to biochemical and pathogenicity tests, as well as repetitivesequence PCR and fluorescent AFLP analysis in comparison with the reference strain of X.a. pv. corylina NCPPB 2896 (National Collection of Plant Pathogenic Bacteria, York, UK). All isolates from Sardinia and Sicily were starch and esculin-positive, had an oxidative glucose metabolism, and grew at 35°C. Genetic fingerprinting showed a strong similarity of the isolates with NCPPB 2896. Pathogenicity tests, made according to Scortichini et al. (2002), showed that all tested isolates induced wilting of inoculated hazelnut twigs. Re-isolations yielded the same colony type as in the primary isolations. We conclude that the agent of the disease observed in hazelnut orchards in Sardinia and Sicily is X. a. pv. corylina. This is the first report of this pathogen in both islands. Scortichini M., Rossi M.P., Marchesi U., 2002. Genetic, phenotypic and pathogenic diversity of Xanthomonas arboricola pv. corylina strains, question the representative nature of the type strains. Plant Pathology 51: 374-381.