Susceptibility of Some Potato Varieties to Infection with the Common Scab Disease Caused by the Bacteria Streptomyces scabiei

Abstract

Common scab of potato, Solanum tuberosum L. is an important disease in Iraq and globally, causing substantial economic losses by diminishing the marketable quality of potato tubers. This study investigated the prevalence of common scab in the northern and central regions of Iraq during the 2024 spring growing season. A survey of 22 potato fields revealed that all were infected with the disease across various cultivars. 22 bacterial isolates were recovered, using oatmeal agar (OMA) growth medium. Pathogenicity tests on radish seedlings, potato slices, and tobacco leaves identified six highly virulent isolates (CS1, CS11, CS14, CS16, CS17, CS22). Among these, isolate CS17, identified as Streptomyces scabiei, exhibited the highest level of pathogenicity. When tested on eight widely cultivated potato cultivars in Iraq, isolate CS17 caused the highest disease incidence and severity, whereas cultivars ‘El Munda’, ‘Burren’, and ‘Agria’ were intermediate, and ‘Alaska’ cultivar was the least susceptible. These findings provided crucial insights into the virulence of local S. scabiei isolates and the susceptibility of different potato cultivars to this pathogen. The least affected cultivars can be used as an important component in the integrated management of potato common scab.

Keywords:

Common scab, Streptomyces scabiei, pathogenicity, potato varieties.