The study evaluated the Bruker MALDI Biotyper® Sirius RUO library's representation of plant pathogenic bacteria, particularly those listed in EU legislation (EU 2019/2072), to identify gaps and prioritize the generation of additional spectra. By cross-referencing the target bacteria with the library's spectra and considering phylogeny, diversity, and taxonomy, the study aimed to ascertain the library's suitability and identify areas for enhancement with custom spectra entries.  he MALDI Biotyper^® sirius RUO, a bench-top mass spectrometer from Bruker, utilizes laser desorption ionization mass spectrometry coupled with a time-of-flight ion mass analyzer. This instrument identifies bacterial isolates by comparing their mass spectra, obtained post-laser bombardment of treated pure cultures, with reference spectra in its database. The effectiveness of identification is contingent on the diversity of bacteria in the library and the accuracy of the reference spectra. In an initial phase, the National Institute of Biology assessed the comprehensiveness of the MBT Compass Library Revision K (2022) in representing quarantine and significant plant pathogenic bacterial pathogens relevant to Slovenia. Our analysis revealed that the library covers 12 of 14 genera and 15 of 32 species of the plant pathogenic bacteria examined. For species-level identification, the library adequately supports genera such as Curtobacterium, Erwinia, Pantoea, Pseudomonas, Rhodococcus and Xylella. For Clavibacter, Ralstonia and Xanthomonas species-level identification is conditionally feasible, depending on specific species. At the genus level Agrobacterium, Dickeya and Pectobacterium are identifiable with the current library. However, spectra for Liberibacter and Xylophilus are absent, rendering the library unsuitable for their identification. Ongoing experimental validation is assessing the reliability of identifications for selected bacterial species. Concurrently, efforts are being made to augment the library with our own entries. We have already expanded the database to include Pantoea stewartii subsp. indologenes, Ralstonia solanacearum, Ralstonia pseudosolanacearum, and Xylophilus ampelinus. This ongoing work underlines the library's potential and limitations in identifying plant pathogenic bacteria, providing valuable insights for its practical application and enhancement.