Considered one of the most important potato (Solanum tuberosum) pathogens in tropical and subtropical regions, as well as in temperate regions with warmer climate, Ralstonia solanacearum is a species with significant genetic diversity. It has been characterized in a binary system of races and biovars based on the range of host species and on the ability to use carbon sources. The attempts to use genetic resistance as a strategy to control R. solanacearum were shown to be unstable due to climatic changes in different regions and due to the variability of the pathogenic strains. Due to different epidemiological characteristics of the biovars, strains of biovar 2 are more likely to be eradicated in an integrated control system. In a survey performed in four regions where potato is produced in Rio Grande do Sul, isolates of R. solanacearum were obtained from 25 crop fields in ten municipalities. The biochemical analyses of the isolates revealed the occurrence of biovars 1 and 2, the latter being predominant. The isolates obtained were evaluated for their genetic variability by PCR, using repetitive sequences ERIC and BOX and random primers (RAPD). The PCR-ERIC and BOX were able to clearly differentiate the biovars 1 and 2. However, neither analysis was able to demonstrate variability among isolates of biovar 2 and only PCR-BOX showed some degree of variability among isolates of biovar 1. The amplification by RAPD demonstrates the distinction between the biovars and revealed that they show characteristic profiles that are closely related to the region where they were obtained.
genetic variability; ERIC; BOX; biovar; race
