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

Banana anthracnose, caused by <i>Colletotrichum musae</i>, causes substantial postharvest losses worldwide, yet effective biocontrol remains limited. Although <i>Hanseniaspora thailandica</i> shows potential, its direct application provides inadequate control. This study demonstrates that alginate oligosaccharide (AOS) potently enhances the biocontrol efficacy of <i>H. thailandica</i> Lg 3 against this disease. Through in vivo fruit assays, <i>H. thailandica</i> 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 <i>C. musae</i> expansion. Furthermore, AOS boosted the activity of critical antioxidant enzymes (CAT, SOD, GPX) in <i>H. thailandica</i> Lg 3 under in vivo conditions. RNA-seq analysis of <i>H. thailandica</i> 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 <i>H. thailandica</i> 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.