Characterization of Bacterial Strains Isolated from Cankers and Exudates on Hazelnut in Sardinia

In the last three years several bacterial isolates have been obtained from cankers and exudates observed on “Tonda Gentile delle Langhe” and “Tonda Gentile Romana” hazelnut cultivars (Corylus avellana L.) cultivated in Sardinia (Italy). Ten representative isolates with fluorescent pigments on the medium B of King et al. (1954), hypersensitive reaction on tobacco leaves and variable levan production, were chosen for pathogenicity tests and serological and molecular characterization. All the isolates were pathogenic to hazelnut, bean, pepper, tomato and pear seedlings, albeit to differing extents. Eight out of ten caused watersoaking on bean pods, while they were weakly pathogenic on lemon fruits and young apricot, peach and walnut plants. No symptoms were observed on lilac and apple. All ten isolates were tested in ELISA. Six isolates reacted positively to an antiserum (NCPPB 281) against a Pseudomonas syringae type strain, while only five isolates reacted to an antiserum against P. savastanoi pv. phaseolicola. Repetitive PCR with ERIC and BOX primer sets showed that the isolates were different from Pseudomonas avellanae, P. syringae pv. syringae and P. savastanoi pv. phaseolicola. Biochemical and pathogenicity tests, molecular characterization and other comparative studies, showed the 10 isolates obtained in Sardinia belong to a new pathovar whose complete characterization is currently under way.