Inhibitory effect of Origanum vulgare L. essential oil and Bacillus subtilis antagonist on blue mold (Penicillium expensum) and post-harvest quality parameters of sweet cherry (Prunus avium L.)

Fruit rot caused by the pathogenic fungus Penicillium is one of the most critical factors in reducing the post-harvest life of fruit crops worldwide. In the present study, the effects of marjoram essential oil and Bacillus bacteria on the control of rot caused by a blue mold of cherry (Prunus avium L.) in the horticultural laboratory of Urmia University was evaluated. Marjoram essential oil was extracted at the flowering stage by Clevenger apparatus and hydro-distillation. First, cherry fruits were infected with mushroom suspension at a concentration of 105 ha/ml. Then, experimental treatments, including suspension with a concentration of 108 ha/ml selected strains of antagonist bacteria and marjoram essential oil, were applied at five levels of concentration (0, 250, 500, 750, and 1000 μl/l). The fruits were stored in the refrigerator at a temperature of 0 °C and relative humidity of 90-95% for 30 days. Finally, different qualitative traits including titratable acidity, pH, soluble solids, tissue firmness, weight loss, antioxidant activity (DPPH) and fungal rot of the fungus were evaluated at three times (0, 15 and 30 days) and in three replications. The marjoram essential oil at a concentration of 750 μl/l and Bacillus bacteria was the most effective treatment in maintaining titratable acidity, lowering pH and soluble solids on the 15th day. Also, antioxidant activity was enhanced by increasing the concentration of marjoram essential oil. The lowest rate of fruit weight loss was observed at a concentration of 500 μl/l of essential oil during the 15th day. According to our findings, marjoram essential oil compounds, especially carvacrol, as well as Bacillus bacteria, as natural compounds and guaranteeing human health, can be suggested as alternatives to chemical compounds in the control of pathogenic fungi in fruit products.