AUTHOR=Sun Zihao , Hao Baihui , Wang Cuicui , Li Shiyu , Xu Yuxin , Li Baohua , Wang Caixia 

TITLE=Biocontrol features of Pseudomonas syringae B-1 against Botryosphaeria dothidea in apple fruit

JOURNAL=Frontiers in Microbiology

VOLUME=14

YEAR=2023

URL=https://www.frontiersin.org/journals/microbiology/articles/10.3389/fmicb.2023.1131737

DOI=10.3389/fmicb.2023.1131737

ISSN=1664-302X

ABSTRACT=<p>Apple ring rot caused by <italic>Botryosphaeria dothidea</italic> 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 <italic>Pseudomonas syringae</italic> B-1 against <italic>B. dothidea</italic> and explore its mechanism of action utilizing <italic>in vitro</italic> and <italic>in vivo</italic> assays. The results showed that <italic>P. syringae</italic> 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 <italic>B. dothidea</italic> infection depended on its concentration and the interval time. <italic>P. syringae</italic> B-1 cells showed higher inhibitory activities than its culture filtrates on the mycelial growth and spore germination of <italic>B. dothidea</italic>. Moreover, <italic>P. syringae</italic> B-1 treatment alleviated electrolyte leakage, lipid peroxidation, and H<sub>2</sub>O<sub>2</sub> accumulation in <italic>B. dothidea</italic>-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 (<italic>PR1</italic>, <italic>PR5</italic>, <italic>GLU</italic>, and <italic>CHI</italic>) and two genes involved in the biosynthesis of SA (<italic>SID2</italic> and <italic>PAD4</italic>) to promote the resistance potential in apple fruit. Hence, our results suggest that <italic>P. syringae</italic> B-1 is a promising strategy against <italic>B. dothidea</italic>, mainly through reducing oxidative damage, activating defense-related enzymes, accumulating disease-resistant substances, and triggering the expression of resistance-correlated genes in apple fruit.</p>