Improvement of Biocontrol Efficiency of Hanseniaspora thailandica Induced by Alginate Oligosaccharide Against Banana Anthracnose Caused by Colletotrichum musae.

Banana anthracnose, caused by Colletotrichum musae, causes substantial postharvest losses worldwide, yet effective biocontrol remains limited. Although Hanseniaspora thailandica shows potential, its direct application provides inadequate control. This study demonstrates that alginate oligosaccharide (AOS) potently enhances the biocontrol efficacy of H. thailandica Lg 3 against this disease. Through in vivo fruit assays, H. thailandica Lg 3 that was cultured in AOS-supplemented medium significantly elevated key defense enzymes, specifically ployphenol oxidase (PPO), peroxidase (POD), chitinase (CHI) and β-1,3-glucanase (GLU) in bananas, and enhanced yeast biofilm formation. This led to higher yeast populations in banana wounds and effective suppression of C. musae expansion. Furthermore, AOS boosted the activity of critical antioxidant enzymes (CAT, SOD, GPX) in H. thailandica Lg 3 under in vivo conditions. RNA-seq analysis of H. thailandica Lg 3 revealed corresponding alterations in glutathione metabolism and oxidative phosphorylation pathways following the addition of 10 mg/L AOS to the medium. The 10 mg/L AOS concentration proved most effective, robustly enhancing biocontrol efficacy. Our findings identify AOS-induced H. thailandica Lg 3 as a practical, ready-to-test biocontrol strategy that could be developed into a commercial formulation to reduce chemical fungicide dependence in postharvest banana protection.