Biocontrol features of B-1 against in apple fruit.

Apple ring rot caused by is an important disease that leads to severe quality deterioration and yield loss at pre-harvest and postharvest stages. Therefore, it is urgent to develop safe and efficient measures to control this disease. The objective of the present study was to investigate the biocontrol features of B-1 against and explore its mechanism of action utilizing and assays. The results showed that B-1 strongly reduced the incidence of apple ring rot and lesion diameter by 41.2 and 90.2%, respectively, in comparison to the control fruit. In addition, the control efficiency of strain B-1 against infection depended on its concentration and the interval time. B-1 cells showed higher inhibitory activities than its culture filtrates on the mycelial growth and spore germination of . Moreover, B-1 treatment alleviated electrolyte leakage, lipid peroxidation, and HO accumulation in -infected apple fruit by increasing antioxidant enzyme activities, including peroxidase, catalase, superoxide dismutase, and ascorbate peroxidase. We also found that strain B-1 treatment enhanced four defense-related enzyme activities and stimulated the accumulation of three disease-resistant substances including phenolics, lignin, and salicylic acid (SA) in apple fruit. In addition, strain B-1 triggered the upregulated expression of defense-related genes such as PR genes (, , , and ) and two genes involved in the biosynthesis of SA ( and ) to promote the resistance potential in apple fruit. Hence, our results suggest that B-1 is a promising strategy against , mainly through reducing oxidative damage, activating defense-related enzymes, accumulating disease-resistant substances, and triggering the expression of resistance-correlated genes in apple fruit.