ε-Poly- -lysine delayed the passion fruit rot development by affecting the oxidative stress, AsA-GSH cycle and membrane lipid components

Lasiodiplodia theobromae is a major pathogen that seriously causes the fruit rot and reduces the postharvest quality of passion fruit. ε-PL, as an effective antifungal agent, exhibis strong inhibitory activity against the postharvest rot of fruits. This study investigated how ε-PL mitigated L. theobromae-induced passion fruit rot development, involving effects on oxidative stress, AsA-GSH cycle and membrane lipid component contents. Compared to L. theobromae-infected passion fruit, ε-PL reduced the lesion diameter and disease index of the fruit, thereby delaying the passion fruit rot onset. Furthermore, ε-PL decreased the CMP and contents of O₂^-., H₂O₂ and MDA, while increasing the activities of SOD, CAT and POD, as well as the levels of total phenolics, flavonoid, reducing power and DPPH radical scavenging ability of L. theobromae-infected passion fruit. Additionally, ε-PL-treated L. theobromae-infected passion fruit revealed higher activities of DHAR, APX, GPX, MDHAR and GR, along with greater levels of GSH, GSSG and AsA, lower content of DHA, and higher ratios of GSH/GSSG and AsA/DHA. Besides, ε-PL raised the levels of USFAs, FAs unsaturation, PI and PC, reduced the activities of PI-PLC, lipase, PC-PLC, PLD and LOX, and decreased the amounts of DAG, PA and SFAs in L. theobromae-infected passion fruit. Therefore, ε-PL delayed passion fruit rot development caused by L. theobromae. The underlying mechanism involved ε-PL enhancing activity of AsA-GSH cycle and reducing modification of membrane lipid components, thereby alleviating oxidative stress and preserving cell membrane structure.