Use of Indigenous <i>Bacillus velezensis</i> Strain BK17 in the Control of Sugar Beet Pathogen <i>Pseudomonas syringae</i> pv. <i>aptata</i>

Bacterial leaf spot of sugar beet (Beta vulgaris L.), caused by bacterium Pseudomonas syringae pv. aptata, threatens the sugar beet industry worldwide. Isolations of a suitable biocontrol agent from the sugar beet phyllosphere conducted in this study led to the discovery of a highly effective strain BK17. Based on 16S rRNA gene sequencing, along with tuf, gyrA, and yngG gene analyses, as well as sequencing of genes involved in the biosynthesis of antimicrobial lipopeptides (fenD-2, bamC, sfp, srfAB, and ituA-B), strain BK17 was identified as Bacillus velezensis. Biological efficacy of strain BK17 was demonstrated on sugar beet (cv. ‘Viola’) plants by applying it in the early plant growth stages, as a part of pot (BBCH 10) and field (BBCH 15-16) experiments, and preventively, 24 hours before inoculation with six P. syringae pv. aptata strains, four of which originated from Serbia and two were reference strains from the Netherlands. These treatments demonstrated the high potential of strain BK17 in the suppression of bacterial spot disease, as reflected in 75.14–82.75% and 66.12–85.10% efficacy in pot and field experiments, respectively. This research enriches the current knowledge of B. velezensis utilization in the biocontrol of bacterial leaf spot, providing a foundation for future studies aimed at promoting sustainable agriculture within integrated pest management strategies.