There are three published different taxonomic level for strains within the same species of Xanthomonas. Pathological variant (pv.) is the most accepted, "variant" (var.) is present for some groups like X. citri pv. phaseoli var. fuscans*, and "subspecies" (sbsp.)were designated for groups within X. citri and others.

"The list of plant pathogens which cannot be differentiated by means of phenotypic (lab.) characters, but have been used by plant pathologists for naming differentiable diseases, was rejected by the ICSB who did not wish to include the taxon pathovar" (Dye, D. W., et al. "International standards for naming pathovars of phytopathogenic bacteria and a list of pathovar names and pathotype strains." Review of Plant pathology 59.4 (1980): 153-168.)

Which is correct to use?

* Look for example: Ariute, J.C.; Rodrigues, D.L.N.; de Castro Soares, S.; Azevedo, V.; Benko-Iseppon, A.M.; Aburjaile, F.F. Comparative Genomic Analysis of Phytopathogenic Xanthomonas Species Suggests High Level of Genome Plasticity Related to Virulence and Host Adaptation. Bacteria 2022, 1, 218-241. https://doi.org/10.3390/bacteria1040017