Effects of Plant Essential Oil Treatment on the Growth of Pathogenic Fungi and the Activity of Defense-Related Enzymes of Fungi-Inoculated Blueberry

Abstract

Fungal decay is one of the most significant causes of postharvest losses of blueberries, with Botrytis rot caused by Botrytis cinerea and Alternaria rot caused by Alternaria alternata being the two most destructive fungal diseases. Plant essential oil has attracted the extensive attention of scholars due to its natural antifungal and anti-corrosion effects. In this study, the effects of fumigation treatment with plant essential oils on the growth of pathogenic fungi in blueberry fruits in vitro and the activity of defense-related enzymes of fungi-inoculated blueberry were evaluated. The results showed that, of the six natural plant essential oils of cinnamon, oregano, clove, tea tree, pomelo peel, and rosemary, oregano essential oil had the most efficient inhibitory effect on Botrytis cinerea and Alternaria alternata in PDA. After fumigating inoculated blueberry fruits with concentration gradients of 0, 30, 60, and 90 μL/L of oregano essential oil, it was found that the activity of defense-related enzymes such as phenylalanine ammonia lyase (PAL), polyphenol oxidase (PPO), peroxidase (POD), chitinase (CHI), and β-1,3-glucanase (GLU) in the inoculated blueberry fruits was induced and enhanced to varying degrees throughout the entire storage period, effectively enhancing the resistance of blueberry fruits to pathogenic fungi and reducing the postharvest decay caused by Botrytis cinerea and Alternaria alternata. The optimal concentration for the fumigation treatment with oregano essential oil is 60 μL/L. This study provides a theoretical basis for the postharvest application of oregano essential oil in blueberries and other fruits and vegetables.