Research on the Isolation of Endophytic Fungi from Papaya and the Prevention of Colletotrichum gloeosporioides

Endophytic fungi can be used as a source of herbal antioxidants to overcome the limitations of low yield and lengthy growth cycles associated with using plants as raw materials for antioxidant production. Papaya fruit is often susceptible to infection by <i>Colletotrichum gloeosporioides</i> after harvest, leading to postharvest rot. Endophytic fungi were extracted with ethyl acetate, and the initial screening concentration was 100 mg/L. Seven strains were identified, with scavenging rates exceeding 50% and strong antioxidant activity. The IC50 values in DPPH and ABTS free radical scavenging assays ranged from 19.72 to 84.06 mg/L and from 14.34 to 64.63 mg/L, respectively. Strain Y17 exhibited robust antioxidant activity (IC50 < 20 mg/L) and was identified as <i>Penicillium rolfsii</i> (MT729953) through ITS sequencing. Treatment of papaya fruit wounds with a fermentation broth of strain Y17 significantly inhibited the infection and colonization of anthracnose pathogens, resulting in a slowed disease incidence rate. This promoted the activity of protective enzymes, such as CAT, POD, and SOD, in the papaya fruit and slowed down the rate of MDA accumulation. This strain, which was found to have antioxidant activity in this study, has the potential to control anthracnose in papaya and has value in terms of further development and utilization.