Identification and Separation of Potato soft rot with Morphological, Biochemical and Molecular Methods from Isfahan Province

Potato soft rot is a common and important disease on potatoes. Fifteen pectolytic bacteria with green metallic colonies on EMB medium were isolated from the tubers showing surface cracking and soft rot symptoms, simultaneously. All the isolates grew at 37 ˚C, no starch digestion, they were not sensitive to erythromycin and negative for phosphatase. They could not use sugars of Xylose, Trehalose, α-methyl D-glycoside and Malonate, while they were able to use Inositol, Rhamnose and Arabitol sugars. Based on These characteristics the isolates recognized as P. carotovorum subsp. carotovorum. The isolates were further identified by PCR amplification with primer G1/L1 which produces two bands similar to those produced in P. carotovorum subsp. carotovorum, but not from P. carotovorum subsp. atrosepticum and Dickeya chrysanthemi. Digestion of the amplified PCR product with restriction enzyme Rsa I resulted in identical 385 bp, 280bp and 180 bp bands formation as described for P. carotovorum subsp. carotovorum. The results of physiological, pathogenicity, biochemical and molecular tests, confirmed that all bacterial isolates induced soft rot symptoms in potato tubers are P. carotovorum subsp. carotovorum.