Molecular characterization and copper susceptibility of Xanthomonas citri subsp. citri strains obtained in Northeast Brazil

The first occurrence of Asiatic citrus canker in Brazil was recorded in the 1950s in the Southeast region. However, the disease has only spread to citrus-producing areas in the Northeast of the country in recent years. Thus, aiming to investigate the variability among 142 strains from this region, we carried out a polyphasic characterization using phenotypic, molecular, phylogenetic, and pathological analyses. All strains showed identical rep-PCR profiles and caused typical symptoms of Asiatic citrus canker on Citrus sinensis , C. latifolia , and C. paradisi , and were characterized as pathotype Xcc-A. A Bayesian inference tree built from concatenated sequences of the gyrB , rpoD , fyuA , and dnaK genes enabled precise identification of the strains as Xanthomonas citri subsp. citri . Strains representative of different Northeast states showed an identical biochemical profile, were more sensitive to copper oxychloride than to copper hydroxide, and only the copL gene was detected. Cross-inoculation experiments indicated that X. citri subsp. citri can cause lesions and survive on the leaves of Anacardium occidentale , Schinus terebinthifolia , and Mangifera indica for more than 10 days. Together, our results showed the strains of X. citri subsp. citri used in this study exhibited high genetic homogeneity based on rep-PCR and MLSA, suggesting a predominantly clonal population structure, with copper resistance currently uncommon among the evaluated strains. In addition, we demonstrated that non-Rutaceae plants could serve as a temporary host for the pathogen.