00 Testo

The amplified fragment length polymorphism (AFLP) technique was applied to 109 strains of pv. pruni and one strain of pv. juglandis of the species Xanthomonas arboricola and to five strains of other Xanthomonas species. Groups of 12 and 41 strains of pv. pruni were isolated at the same time from fruit lesions in two peach orchards in the province of Verona (Italy). The other strains of pv. pruni were from different geographic areas and/or host plants. The EcoRI/MseI and EOO/M02 pairs were used as restriction enzymes and selective amplification primers. Comparison of the AFLP profiles showed that the X. arboricola pv. pruni profile could be reliably distinguished from those of pv. juglandis and the other five species; 108 out of 109 strains of X. arboricola pv. pruni were included in the main cluster (SD = 0.93). This was divided into 3 subgroups: I (SD = 0.982; 73 strains); II (SD = 0.979; 32 strains); III (SD = 0.990; 3 strains). Another subgroup, IV, with just one strain clustered with the other 3 subgroups at SD = 0.89. Isolates from the same peach orchard fell within subgroups I and II, as did strains from other geographic areas or from different host plants. The technique used did not have sufficient resolution to distinguish homogeneous groups of pv. pruni of X. arboricola on the basis of locality, geographic area or host plant.