Sequevar distribution of Ralstonia spp. in Solanaceae in the semiarid climate of the Pernambuco state, Brazil

The phylogenetic relationships and distribution of Ralstonia pseudosolanacearum and Ralstonia solanacearum sequevars were analyzed in 108 strains of Solanaceae in three mesoregions of the Pernambuco State, Brazil. These mesoregions are characterized by a semiarid climate and account for 88.20% of the area of the state. Ralstonia pseudosolanacearum (phylotype I, biovar 3) was predominant in Agreste, and R. solanacearum (phylotype II, biovar 1) was predominant in São Francisco and Sertão. Two haplotypes of R. pseudosolanacearum were identified by analysis of the haplotype network of the partial egl gene sequences and were phylogenetically related to sequevars I-17 and I-18. Five haplotypes of R. solanacearum were identified; two haplotypes were related to sequevar IIA-50, and three haplotypes were related to new sequevars IIA-61, IIA-62, and IIA-63. In Brazil, sequevars I-17, IIA-61, IIA-62, and IIA-63 were detected exclusively in the semiarid climate of Pernambuco, unlike sequevars I-18 and IIA-50, which were detected in other regions of Brazil. Furthermore, R. pseudosolanacearum (phylotype I) and sequevar IIA-50 were detected in the Sertão mesoregion. Sequevar I-18, IIA-61, and IIA-62 strains were prevalent in the Agreste mesoregion, and sequevars I-17 and IIA-50 were prevalent in the São Francisco mesoregion. The virulence variability of the strains toward tomato was related to species and sequevars. Introduced R. pseudosolanacearum strains of sequevar I-18 had higher estimated virulence compared to that of the native R. solanacearum strains of sequevar IIA-50. This is the first study that analyzes the variability of Ralstonia spp. in the semiarid region of Brazil.