MULTILOCUS SEQUENCE ANALYSIS OF RALSTONIA SOLANACEARUM ISOLATES ORIGINATED FROM POTATO IN SERBIA

Abstract

Ralstonia solanacearum is a soil borne bacterium which affects more than 450 plant species including a wide range of crop plants, ornamentals and weeds. This bacterium is causing bacterial wilt disease which leads to severe economic losses. On potato, disease is known as brown rot. Even though this phytopathogen originates from tropic, subtropics and warm temperate regions, in recent years cold-adapted strains dramatically enhanced the threat of European potato crops, including Serbia. R. solanacearum is at A2 list of quarantine plant pathogens in Europe. During six year period (2013-2018), isolates from diseased potato tubers were collected, identified using Multilocus sequence analysis (MLSA) and checked for certain phylotype affiliation. DNA from the obtained isolates was amplified using seven housekeeping genes (adk, fliC, gapA, gdhA, gyrB, hrpB, ppsA) and sequenced. Phylogenetic analysis was performed with concatenated sequences of all tested isolates, and compared with the most similar R. solanacearum strains from PAMDB database. All Serbian isolates were identified as R. solanacearum using PAMDB BLAST. Neighbor-joining phylogenetic analysis placed tested isolates in the same cluster with R. solanacearum strains belonging to race 3, biovar 2, and phylotype II obtained from PAMDB. Although, bacterial wilt caused by this plant pathogenic bacteria is appearing in different locations and on different potato cultivars in Serbia it remained genetically homogenous. Currently, R. solanacearum is a quarantine bacteria occurring only on potato in our country, but considering its wide host range, there is a possibility of it causing disease on other significant crops with devastating consequences. Therefore, its fast and accurate identification and mapping is of main interest for stopping the disease spread.