Draft Genome Sequences of Pseudomonas syringae pv. tomato Strains J4 and J6, Isolated in Florida.

Pseudomonas syringae pv. tomato causes bacterial speck in tomato. We report the genome sequences of two P. syringae pv. tomato strains, J4 and J6, that are genetically closely related, with >99.9 average nucleotide identity (ANI), but vary in the presence of coronatine-associated genes.

Multiple Recombination Events Drive the Current Genetic Structure of Xanthomonas perforans in Florida.

Prior to the identification of Xanthomonas perforans associated with bacterial spot of tomato in 1991, X. euvesicatoria was the only known species in Florida. Currently, X. perforans is the Xanthomonas sp. associated with tomato in Florida. Changes in pathogenic race and sequence alleles over time signify shifts in the dominant X. perforans genotype in Florida. We previously reported recombination of X. perforans strains with closely related Xanthomonas species as a potential driving factor for X. perforans evolution. However, the extent of recombination across the X. perforans genomes was unknown. We used a core genome multilocus sequence analysis approach to identify conserved genes and evaluated recombination-associated evolution of these genes in X. perforans. A total of 1,356 genes were determined to be "core" genes conserved among the 58 X. perforans genomes used in the study. Our approach identified three genetic groups of X. perforans in Florida based on the principal component analysis (PCA) using core genes. Nucleotide variation in 241 genes defined these groups, that are referred as Phylogenetic-group Defining (PgD) genes. Furthermore, alleles of many of these PgD genes showed 100% sequence identity with X. euvesicatoria, suggesting that variation likely has been introduced by recombination at multiple locations throughout the bacterial chromosome. Site-specific recombinase genes along with plasmid mobilization and phage associated genes were observed at different frequencies in the three phylogenetic groups and were associated with clusters of recombinant genes. Our analysis of core genes revealed the extent, source, and mechanisms of recombination events that shaped the current population and genomic structure of X. perforans in Florida.

Citrus leprosis resistance within the citrus group.

Reported in Brazil since the 1930's, citrus leprosis, caused mainly by citrus leprosis virus C, has been a major concern for the national sweet orange production. In recent years, the disease has spread to several other countries and it is now considered a worldwide threat. The occurrence of the disease has been studied almost exclusively in sweet oranges because other citrus genotypes are of secondary relevance in Brazil and in some other American countries where it occurs. Here we report 12 resistant citrus genotypes among 160 accessions evaluated. After 90 days of the infestation with viruliferous mites, asymptomatic genotypes were observed in sour orange, lemon, grapefruit, mandarins, tangelo, and tangor groups. The results revealed promising genotypes resistant to the disease, which can be incorporated in citrus breeding programs aiming to obtain varietal resistance, and confirmed the susceptibility of many citrus genotypes to CiLV-C. This assay ratify the already reported uneven level of susceptibility within the citrus group.