| Summary: | Grapes (<i>Vitis vinifera</i> L.) are an essential crop for fresh consumption and wine production. Vineyards are attacked by several economically important bacterial and fungal diseases that require regular pesticide treatment. Among them, <i>Pseudomonas syringae</i> pv. <i>syringae</i> (<i>Ps. syringae</i>) and <i>Botrytis cinerea</i> (<i>B. cinerea</i>) infections cause huge economic losses. The fresh fruit market has shifted to functional natural foodstuffs with clear health benefits and a reduced use of chemicals along the production chain. Lactic acid bacteria (LAB) have a biopreservative effect and are applied to ensure food safety in response to consumers’ demands. In the present study, the possibilities of using microorganisms with a potential antimicrobial effect against <i>Ps. syringae</i> and <i>B. cinerea</i> in the production of table grapes were investigated. LAB of the genus <i>Lactiplantibacillus</i> can be a natural antagonist of pathogenic bacteria and fungi by releasing lactic acid, acetic acid, ethanol, carbon dioxide and bacteriocins in the medium. The present study focuses on the characterization of nine <i>Lactiplantibacillus plantarum</i> (<i>Lp. plantarum</i>) strains isolated from spontaneously fermented sourdoughs. Species-specific PCR identified the isolated LAB for partial <i>recA</i> gene amplification with an amplicon size of 318 bp. RAPD-PCR analysis showed the intraspecific diversity of the individual strains. Thirteen plantaricin-like peptides (PlnA, PlnB, PlnC, PlnD, PlnEF, PlnG, PlnI, PlnJ, PlnK, PlnN, PlnNC8, PlnS, and PlnW) produced by isolated <i>Lp. plantarum</i> strains were detected by PCR with gene-specific primers. The key features for future industrial applications were their antimicrobial properties. The culture medium and cell-free supernatant (CFS) were used to establish in vitro antimicrobial activities of <i>Lp. plantarum</i> strains against <i>Ps. syringae</i> and <i>B. cinerea</i>, and inhibition of phytopathogen development was observed. The inhibitory effect of the CFS (cell-free supernatant) of all strains was assessed by infecting table grapes with these pathogens in in vivo experiments. <i>Lp. plantarum</i> Q4 showed the most effective suppression of the pathogens both in vitro and in vivo, which indicates its potential use as a biocontrol agent against berry rot and grey rot on grapes, caused by <i>Ps. syringae</i> and <i>B. cinerea</i>.
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