Variability and genetic diversity among Streptomyces scabiei infected potato cultivars with common scab from Egypt

Twelve isolates of the Streptomyces scabiei causing the common scab in potato were isolated from potato plants originated from different governorates in Egypt. In order to study genetic variation among, these isolates a total of 5 random ten-mer primers were used to perform the Random amplified Polymorphic DNA RAPD-PCR profiles for these 12 isolates. The results revealed that these primers were able to produce different bands. The number of amplified bands varied between 7 to 14, and the size ranged from 247 to 2226 bp. RAPD molecular technique showed that these isolates could be grouped in two clusters. First cluster included the highest value of similarity (81%) between strain No. 9 and strain No. 12; while in second cluster isolates No.1, 2, 3, 4, 5, 6 and 7 were pertained to Aswan, Elminia and Assiut regions with similarity value of 40 %. Under open greenhouse conditions, reaction of certain potato cultivars to common scab infection was evaluated. Lady Rosetta cultivar exhibited the lowest susceptibility to disease by 62.67 followed by Cara cultivar with 58.33. While Diamont, Mondial and Spunta cultivar showed the least degree of scab symptoms. Cara contained the highest concentration of total sugar. Lady Rosseta contained the highest concentration of pectin substances 0.684. Diamont cultivar contained the highest concentration of calcium (0.105 mg/L), and Spunta contained the highest concentration of potassium (2.33 mg/L), while Mondial, contained the highest concentration of sodium (1.28 mg/L). These results showed that potato cultivars varied in their susceptibility to common scab disease and further studies are required to determine the factors responsible for resistance or susceptibility.