FIRST REPORT OF POTATO BROWN ROT CAUSED BY RALSTONIA SOLANACEARUM IN GEORGIA

Abstract

Potato is one of the most important constituent of the human diet in Georgia. Potato brown rot caused by Ralstonia solanacearum is an economically important bacterial disease and the cause of severe damage to the potato industry. During 2011-2013 a survey of potato plantations and storage facilities in different potato-producing regions of Georgia, samples were collected of tubers with brown rot symptoms and wilted potato leaves and stems. Since 2010, bacterial wilt presumed to be caused by R. solanacearum has been an important disease in Georgia. The disease was first reported in tomato in Chkorotsku and Kutaisi regions (west Georgia), where it caused up to 100% plant loss in greenhouse- and field-grown crops (Meparishvili, et al., 2012). Since then, several cases of this disease have been documented on potato in home gardens in the Kobuleti region. In 2012 -2013, brown rot symptoms were detected in several commercial potato cultivars. i.e. Jelly, Marfona, Picasso, Finca, Agria, Alliance, Marabely in Khulo (west Georgia) and Akhaltsikhe (south Georgia). Bacteria isolated from wilted potato plants and rotten tubers produced typical pearly white, flat, irregular, fluidal colonies on CPG and fluidal, irregular in shape and milky white colonies with pink centers on SMSA media, respectively. These colonies were presumed to belong to R. solanacearum, thus their identity was sought and confirmed by specific PCR using the primer pair OLI/Y2 (Seal et al., 1993). All tested isolates and positive control DNA extracted from R. solanacearum type strain NCPPB 325 produced the expcted 288 bp product, confirming their identity as Ralstonia solanacearum. To the best of out knowledge, this is the first report on the presence of potato brown rot in Georgia.