Evaluation of repeat sequences on plasmid pEA29 of Erwinia amylovora from Iran

The plasmid content of 38 Iranian Erwinia amylovora strains isolated from five different plant species and geographical locations from 2005 to 2013 were evaluated. With exception to the pEA29 plasmid, isolates obtained from quince and hawthorns carry the pEU72 plasmid. RFLP analysis of PstI amplified fragment of plasmid pEA29 using HpaII revealed three known fragments in all strains. Based on the observed polymorphism in the larger one that varied between 360 to 400 bp, all Iranian strains clustered into four groups. In order to determine the exact number of short-sequence DNA repeats, 18 strains were chosen for PstI fragment sequencing. About 63 % of the strains carried a repeat number of 4. The remaining 37 % harboured five, seven and eight repeats. Sometimes a correlation was seen between the RFLP patterns and SSR grouping with respect to other factors including the host plant species, geographical region or sampling year. This study reported the genetic variation of E. amylovora strains for the first time in Iran, based on enzymatic digestion of the PstI fragment of pEA29 and evaluation of the short sequence repeat units. It seems that, the latter method may be reliable for E. amylovora strains grouping.