Abstract
Abstract This study investigated the antagonistic potential of the lactic acid bacterium Lacticaseibacillus paracasei 22 against major pathogens causing postharvest diseases of apple fruit. The main biologically active components of the strain culture broth were identified as 2,3-butanediol. Acetoin, and organic acids, particularly lactic and acetic acids, all of which exhibited toxic activity against the tested phytopathogens. The biological efficacy of an experimental biopreparation based on L. paracasei 22 was evaluated both in vivo and in vitro conditions. Pre-treatment of healthy apple fruit by immersion in the culture broth of L. paracasei 22 supplemented with Tween 20 prior to artificial inoculation with fungal pathogens resulted in a statistically significant reduction in disease development compared with the untreated control. Evaluation of different application methods and fruit-storage conditions under commercial roduction conditions showed that spraying apple trees with the biopreparation at commercial maturity, before he fruit was placed in long-term storage, substantially reduced disease incidence and provided prolonged protection during storage. These findings demonstrate the potential of the biopreparation applied at a concentration 109 CFU mL−1 as an effective biological control agent against various types of apple fruit rot. Its application may contribute to reducing crop losses both before harvest and during long-term storage.