Hybrid Genome Reanalysis of Bacteriophage XaF13 Infecting Xanthomonas vesicatoria Provides Insights into Its Phylogenetic Relationships Within the Family Inoviridae

Bacteriophages infecting phytopathogenic bacteria represent promising alternatives for plant disease control; however, some groups, such as filamentous bacteriophages, remain comparatively underexplored. In this study, we present a comprehensive characterization of XaF13, a filamentous bacteriophage that infects Xanthomonas vesicatoria, the causal agent of bacterial spot disease in pepper. Morphological analysis revealed a flexible filamentous virion architecture consistent with members of the family Inoviridae. To refine its genomic features, the XaF13 genome was resequenced through a hybrid approach combining newly generated Oxford Nanopore long reads with previously available Illumina data, resulting in a revised genome of 6965 bp. Comparative genomic analysis and intergenomic similarity assessment revealed low nucleotide identity with related inoviruses, supporting the recognition of XaF13 as a putative novel species based on VIRIDIC species-level thresholds. Phylogenetic reconstruction based on the Zot-like protein placed XaF13 within a broader inovirus lineage and showed that it forms a distinct evolutionary branch. In addition, physicochemical assays revealed that XaF13 remains stable across a broad pH range and tolerates brief exposure to elevated temperatures, whereas chloroform treatment and UV-C radiation reduced viral infectivity over time. Overall, these findings highlight the genomic distinctiveness and in vitro physicochemical stability of XaF13, contribute to a better understanding of filamentous bacteriophage diversity and provide a basis for future studies on its ecological role and possible interactions with phytopathogenic bacteria.