Mechanisms of Priestia megaterium PH3 in alleviating postharvest disease caused by Penicillium expansum in Nanguo pear fruit

Penicillium expansum is one of the primary pathogens causing rot in fruit and vegetables. The progression of blue mold damages the appearance and nutritional value of produce, leading to significant economic losses. Recent studies have shown that endophytes, as a vital component of potential microbial agents, can control various fungal diseases. This study focuses on the inhibitory mechanism of the peanut endophyte Priestia megaterium PH3 against blue mold in Nanguo pear. The results demonstrated that the endophytic P. megaterium PH3 and its metabolites not only inhibit the spore germination of P. expansum. Most notably, after rapidly colonizing the surface of Nanguo pear fruit, P. megaterium PH3 enhances the activity of antioxidant enzymes (SOD, CAT, APX, MDHAR, DHAR and GR) and non-enzymatic antioxidants (AsA and GSH), suppressing the ROS surge caused by P. expansum infection. Additionally, the P. megaterium PH3 upregulates the activity of enzymes (PAL, C4H, 4CL, PPO and POD) and gene expression (PuPAL, PuC4H and Pu4CL) related to phenolics metabolism, promoting the synthesis and metabolism of phenolics and flavonoids compounds, effectively inhibiting the onset of blue mold in Nanguo pear. These findings indicate that P. megaterium PH3 is a promising and effective microbial agent for mitigating postharvest blue mold in Nanguo pear.