CHARACTERIZATION OF PSEUDOMONAS POPULATIONS ISOLATED FROM HAZELNUT (CORYLUS AVELLANA) TREES IN SARDINIA (ITALY)

Studies on hazelnut in Sardinia showed the presence of different bacterial populations (Xanthomonas arboricola pv. corylina, Pseudomonas syringae pv. syringae and P. syringae pv. coryli) causal agents of dieback. In field surveys carried out in autumn and spring 2014-2015 in the central part of Sardinia (Barbagia di Belvì), on hazelnut cultivations, were observed plants showing atypical symptoms characterized by the presence of necrosis along leaf veins and young shoots and atypical canker lesions, with or without hypertrophies, on one/two years old branches. Twenty-five isolates obtained from tissues with symptoms were characterized, four, on sucrose nutrient agar, were levan positive, instead the others twenty-one were negative. All isolates induced a hypersensitivity reaction on tobacco leaves, were pathogens, with different degrees, on hazelnut plantlets and showed a different pathogenic reaction on tomato and bean seedlings. The isolates were assessed for serological slide agglutination test using an antiserum from Pseudomonas syringae van Hall: 20 of them showed a positive reaction. Metabolic profile performed by Biolog GEN III microplates showed that all the twenty- five isolates belong to Pseudomonas genus. In particular: three of them were P. caricapapayae, two P. fluorescens, five P. syringae, five P. syringae pv. tabaci, ten P. syringae pv. anthirrini. These latter were characterized to grow on lincomycin, vancomycin, rifamycin sv, quinic acid, 1% sodium lactate, tetrazolium violet, tetrazolium blue, niaproof 4, potassium tellurite and pH 6. Molecular characterization of these bacteria as well as further tests to determine their pathogenic role are currently underway.