This study was conducted to evaluate the efficacy of the Lactobacillus plantarum A7 (L. Plantarum), ajwain and cinnamon essential oils (AO and CO, respectively) in suppressing gray mold rot in strawberry fruit. AO and CO showed over 90% inhibition of radial mycelia growth with lower concentration of the oils per plate for all tested pathogens. Combined application of L. plantarum with AO and CO was tested to assess the possible synergistic effects of these 3 elements on the control of tested plant pathogens. In this case both combinations of L. plantarum + AO and L. plantarum + CO inhibited the mycelia growth of the pathogens completely. Results showed that the combined treatment of strawberry fruits with L. plantarum + AO (50 μL) and L. plantarum + CO (100 μL) resulted in remarkably improved control of Botrytis infections, in comparison with application of L. plantarum or essential oils alone. Quality attributes (that is pH, acidity, vitamin C, and total soluble solid) of the strawberry fruits did not change significantly (P < 0.01) when combination of Lactobacillus and essential oils was used. To the best of our knowledge, this is the first report on the effects of combination of a Lactobacillus as an antagonist bacterium with essential oils to increase the shelf life of strawberry.
The combination of antagonist bacteria and essential oils has emerged as a safe alternative to replace synthetic preservatives. According to these findings, the combination of L. plantarum A7 and the essential oils of cinnamon and ajwain can be used as preservative to increase the shelf life of fruits in postharvest stage.