Thirty-Four isolates of Erwinia carotovora subspecies carotovora (Ecc) causing soft rot of potato, were collected from tubers of potato plants grown in North and East Egypt. The frequency of the isolated species of soft rot-associated bacteria, being 10, 10, 8 and 6 isolates from Governorates of Sinai, Sharqia, Gharbia and Beheira, respectively. The isolates were identified as Ecc by biochemical method and molecular identity then was confirmed by polymerase chain reaction (PCR) using specific primers FEc1 and REc1 which amplified the Eca-specific band of 690-733 bp. Pathogenicity test divided these 9 isolates into 3 aggressiveness groups, High infection (2 isolates), moderate infection (5 isolates) and low infection (2 isolates), receptively. These isolates were also characterized using the technique of Inter Simple Sequence Repeats polymerase chain reaction (ISSR-PCR) found that 61 amplified fragments, 56 were polymorphic (91.8%) and the percentage of polymorphism ranged from 100% (844B) to 84.62% (HB12); the fragment sizes were 224bp to 1.36 kb. The unweighted pair-group method with arithmetical average (UPGMA) cluster analysis based on pairwise genetic similarity coefficient revealed that the similarity between the selected 9 soft rot bacterial isolates ranged from 0.125 between Ec6 and Ec9 to 0.875 between Ec1, Ec3 and Ec4. The average of similarity among genotypes was 0.500 and divided the soft rot isolates into three well-defined clusters showing a great level of genetic diversity. However, these clusters were not specific to aggressiveness groups, origin or special potato variety. Isolates with different aggressiveness levels, originated from different potato varieties participate between the same clusters. This means that the isolates likely derived from the same source population and got scattered from one area to another through their hosts. |
