CHARACTERIZATION OF PSEUDOMONAS SPP. STRAINS, CAUSAL AGENTS OF CANKERS AND WILT ON STONE FRUITS IN SARDINIA.

Isolations made from apricot, nectarine, peach and plum plants showing cankers on twigs, stems and branches, gum exudates, buds’ necrosis, shoots wilted, and spots on leaves allowed us to collect 94 bacterial strains. 13 of them, selected on the basis of morphology on NSA and hypersensitivity reaction on tobacco leaves, were able to infect cherry plum GF31, watermelon and marrow plantlets; two of them pepper and tomato plantlets and five of them lilac and lemon fruits. On the basis of the results obtained by Gram, catalase, Poly--hydroxybutyrate, fluorescence on KB and LOPAT tests, five strains were ascribed to Pseudomonas syringae (Ps); three to P. viridiflava (Pv); four to P. fluorescens; one was not identified. Biolog and serological agglutination tests partially confirmed the results above reported, allowing us even to ascribe three strains of Pseudomonas syringae to the pv. syringae (Pss). The fatty acid analysis of five out of thirteen isolates ascribed one of them to Ps (S.I., 0.967); one to Pv (S.I., 0.979); one to P. putida (S.I., 0.847); while two were not identified. The analysis of the thirteen strains with BOX-PCR produced 5 reaction profiles. One of them was characteristic of the type strain Pss CFBP 700. SyrB gene amplification produced the specific band of 752 bp for the three Pss strains as the type strain Pss CFBP 700, confirming their identification. In conclusion while Pss is already present in Italy in all plant species analyzed, Pv was not yet reported in Europe on apricots and nectarine.