Studio sulle principali malattie batteriche del nocciolo in Sardegna

Investigations on hazelnut showing a state of decline were conducted in Sardinia in 2005- 2007 years and led to the observations of three different symptoms (Type 1-3). On the basis of phenotypic, molecular and fatty acid methyl esters analyses nine isolates (Type 1), which are characterized by the production of green pigments on SQ medium, were assigned to the Xanthomonas arboricola pv. corylina species that is the causal agent of “Bacterial blight”. Twenty-one isolates (Type 2), that cause the twig dieback, were attributed to the species Pseudomonas syringae pv. coryli. They are characterized by the lack of the syrB gene and differ from other isolates collected in Piedmont for several biochemical characteristics and for their fatty acid composition. Twenty-two isolates (Type 3), that are cause of wilting of the twigs and branches, were distinguished in two clearly defined groups: the first comprises thirteen isolates that possess the syrB gene and are similar to P. s. pv. syringae; the second is constituted of nine isolates that can be distinguished for the absence of the syrB gene and for other phenotypic characteristics. In an in vitro preliminary experiment, nine essential oils and five strains of Bacillus amyloliquefaciens were tested against two strains of X. a. pv. corylina, two of P. s. pv. coryli and four of P. syringae. The results of the in vivo experiments evidenced the efficacy of the essential oils obtained from myrtle and thyme and of two isolates of B. amyloliquefaciens in limiting the infections on hazelnut and lemon fruit.