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The family Araceae, comprising ornamentals including Anthurium, Dieffenbachia, Philodendron, Colocasia, and Zantedeschia, is susceptible to Xanthomonas pathogens. Previous analyses have established heterogeneity in aroid strains, yet unresolved taxonomic positions and dynamics between Xanthomonas and frequently associated Stenotrophomonas in aroids necessitate in-depth genetic investigation to resolve these complex relationships. This study utilized multilocus sequence analysis of housekeeping genes atpD, dnaA, dnaK, gltA, and gyrB to investigate 59 aroid strains, selected based on hosts, time, and geographical origins. After adding sequences from additional strains from NCBI GenBank, analysis of 161 concatenated sequences indicated that all aroid strains fell within Xanthomonas and Stenotrophomonas. Thirty-six strains isolated from Anthurium grouped under X. phaseoli, with outliers including one strain each in X. arboricola and X. sacchari and two in Stenotrophomonas. Six strains from Caladium, Dieffenbachia, and Philodendron formed host-specific subgroups within X. euvesicatoria. One strain from Dieffenbachia aligned with X. campestris, whereas strains from Colocasia, Aglaonema, and Spathiphyllum clustered with X. sacchari. Apart from the zantedeschia strain described as X. arboricola pv. zantedeschiae, two colocasia, one epipremnum, and one anthurium strain joined the X. arboricola group. Overall, this study revealed significant heterogeneity among aroid strains, with anthurium strains clustering closely despite distant geographical origins. The analysis underscores the complexity of host-pathogen specificity within Xanthomonas and emphasizes the need for further taxonomic clarification through whole-genome analysis of representative strains. The findings of this research will facilitate strain selection for inclusivity and exclusivity panels in developing diagnostic assays for X. phaseoli and xanthomonads affecting aroids. [ABSTRACT FROM AUTHOR]

Xanthomonas and Stenotrophomonas are closely related genera in the family Lysobacteraceae. In our previous study of aroid-associated bacterial strains, most strains isolated from anthurium and other aroids were reclassified as X. phaseoli and other Xanthomonas species. However, two strains isolated from Spathiphyllum and Colocasia were phylogenetically distant from other strains in the Xanthomonas clade and two strains isolated from Anthurium clustered within the Stenotrophomonas clade. Phylogenetic trees based on 16S rRNA and nine housekeeping genes placed the former strains with the type strain of X. sacchari from sugarcane and the latter strains with the type strain of S. bentonitica from bentonite. In pairwise comparisons with type strains, the overall genomic relatedness indices required delineation of new species; digital DNA-DNA hybridization and average nucleotide identity values were lower than 70 and 95%, respectively. Hence, three new species are proposed: S. aracearum sp. nov. and S. oahuensis sp. nov. for two strains from anthurium and X. hawaiiensis sp. nov. for the strains from spathiphyllum and colocasia, respectively. The genome size of X. hawaiiensis sp. nov. is ~4.88 Mbp and higher than S. aracearum sp. nov. (4.33 Mbp) and S. oahuensis sp. nov. (4.68 Mbp). Gene content analysis revealed 425 and 576 core genes present in 40 xanthomonads and 25 stenotrophomonads, respectively. The average number of unique genes in Stenotrophomonas spp. was higher than in Xanthomonas spp., implying higher genetic diversity in Stenotrophomonas. [ABSTRACT FROM AUTHOR]

The family Araceae, comprising ornamentals including Anthurium , Dieffenbachia , Philodendron , Colocasia , and Zantedeschia , is susceptible to Xanthomonas pathogens. Previous analyses have established heterogeneity in aroid strains, yet unresolved taxonomic positions and dynamics between Xanthomonas and frequently associated Stenotrophomonas in aroids necessitate in-depth genetic investigation to resolve these complex relationships. This study utilized multilocus sequence analysis of housekeeping genes atpD , dnaA , dnaK , gltA , and gyrB to investigate 59 aroid strains, selected based on hosts, time, and geographical origins. After adding sequences from additional strains from NCBI GenBank, analysis of 161 concatenated sequences indicated that all aroid strains fell within Xanthomonas and Stenotrophomonas . Thirty-six strains isolated from Anthurium grouped under X. phaseoli , with outliers including one strain each in X. arboricola and X. sacchari and two in Stenotrophomonas . Six strains from Caladium , Dieffenbachia , and Philodendron formed host-specific subgroups within X. euvesicatoria . One strain from Dieffenbachia aligned with X. campestris , whereas strains from Colocasia , Aglaonema , and Spathiphyllum clustered with X. sacchari. Apart from the zantedeschia strain described as X. arboricola pv. zantedeschiae , two colocasia, one epipremnum, and one anthurium strain joined the X. arboricola group. Overall, this study revealed significant heterogeneity among aroid strains, with anthurium strains clustering closely despite distant geographical origins. The analysis underscores the complexity of host-pathogen specificity within Xanthomonas and emphasizes the need for further taxonomic clarification through whole-genome analysis of representative strains. The findings of this research will facilitate strain selection for inclusivity and exclusivity panels in developing diagnostic assays for X. phaseoli and xanthomonads affecting aroids., Competing Interests: The author(s) declare no conflict of interest.