Bacterial canker of hazelnut (Corylus avellana L.) in Sardinia (Italy): occurrence of Pseudomonas syringae strains

Surveys carried out since the end of 1998 in Sardinia, allowed to ascertain severe die-backs in hazelnut (Corylus avellana L.) orchards. Longitudinal cankers were observed along the twigs and the main branches Sometimes the death of the whole tree was also observed. The hazelnut cultivars recently introduced from the Italian peninsula (Piedmont) such as Tonda Gentile delle Langhe was attacked more than the local cultivars which showed only cankers. Isolations were performed in spring and autumn from symptomatic tissues. Fluorescent colonies on King’s et al. medium B revealed their pathogenicity to hazelnut, pepper, tomato and pear seedlings, and, to a lesser extent, to apricot, peach and lemon fruits. The isolates did not incite any disease in lilac and apple. Biochemical and physiological tests allocated the isolates to the Pseudomonas syringae group Ia sensu Lelliott et al.. Slide agglutination and ELISA tests carried out using an antiserum from P. syringae pv. syringae gave positive results. The isolates were also compared with other pseudomonads associated with hazelnut decline by means of repetitive PCR using BOX primers. The comparison revealed that the isolates obtained in Sardinia were different from P. avellanae, the causative agent of hazelnut decline in northern Greece and central Italy, and from the P. syringae pv. syringae strains previously isolated in Sardinia from local cultivars of C. avellana. The isolates herein studied resemble the P. syringae population recently found in Piedmont and isolated from Tonda Gentile delle Langhe. Other studies are under way to confirm these findings.