Genetic diversity of Xanthomonas citri subsp. citri in citrus orchards in northwest Paraná state, Brazil

Xanthomonas citri subsp. citri, which causes Asiatic citrus canker (ACC), is an important pathogen of citrus in Brazil and elsewhere. The genetic diversity of X. citri subsp. citri pathotype ‘A’ has not been studied in Brazil at a local scale (up to 300 km). Forty isolates were sampled from lesions of ACC on citrus in three orchards in Paraná state, Brazil. Twelve minisatellite markers were used to characterize the genetic diversity of the isolates. An Unweighted Paired Group Method of Arithmetic Averages tree was used for identifying unique multilocus haplotypes but there was no association between haplotypes and source locations. An analysis of molecular variance among populations showed that 98% of the variance was accounted for within the populations, and only 2% was accounted for among populations. Differences among populations was not significant (Φ=0.018, P=0.2). The relatively high, yet uniform, genetic diversity among isolates and low degree of spatial differentiation between populations of X. citri subsp. citri suggests that the populations in Paraná state have a common origin and strong historical epidemiological links