Amylovoran is one of the major virulence factors of a devastating plant pathogen of Erwinia amylovora. Herein, the antibacterial potential of the combined encapsulated plant bioactive compound (Satureja hortensis) and organic acid salt (calcium propionate) was evaluated against E. amylovora, for the first time. To this goal, savory essential oil and calcium propionate were encapsulated using the spray drying technique and then the effects of this formulation on gene expression (amsC) and control of fire blight (inhibiting the amylovoran production) were evaluated. The results of GC/MS analysis showed that O-cymene (25%), terpinolene (18.5%), and carvacrol (2.9%) were the most important compounds in savory essential oil. The highest encapsulation efficiency (96.25%) was provided by optimizing the ratio of maltodextrin to modified starch at 75:25 as the shell of the as-prepared microcapsules. The biocontrol efficiency of this formulation was investigated at three different concentrations T1 (1 g/l formulation), T2 (2 g/l formulation), and T3 (3 g/l formulation), and all treatments significantly impaired the amylovoran production in shoots of pear cv. Spadona. Moreover, among all treatments, T3 caused the greatest decrease in amylovoran gene expression. The reduction of gene expression by T3 was twice more than T2. T3 caused a 2-fold decrease in the expression of the amylovoran gene compared to the internal control gene (16 S rRNA) compared to T2. Also, T2 caused a 2-fold decrease in the expression of the amylovoran gene compared to the internal control gene (16 S rRNA) rather than T1.

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