<i>Meyerozyma caribbica</i> <scp>YDP</scp> ‐27: Biocontrol Agent Tolerance to Oxidative, Osmotic and Temperature Stress for Postharvest Applications

ABSTRACT Postharvest losses due to fungal pathogens pose a significant challenge in fruits and vegetables, especially during storage and transportation of perishable fruits. This study evaluated the efficacy of the phyllosphere yeast Meyerozyma caribbica YDP‐27 in managing postharvest diseases caused by six fungal pathogens: Colletotrichum musae , Colletotrichum capsici , Colletotrichum gloeosporioides , Alternaria alternata , Curvularia alcornii and Pestalotiopsis sp. The yeast demonstrated strong biocontrol potential, with an average mycelial growth inhibition (MGI) of 31.1% across all tested pathogens. The study further explored the effects of environmental stresses, including temperature fluctuations, oxidative stress and osmotic stress, on yeast viability and morphology. High temperatures (38°C and 40°C) and elevated hydrogen peroxide concentration significantly reduced the yeast population. In contrast, the addition of 3% mannitol and ascorbic acid enhanced the yeast's oxidative stress tolerance and viability. Mannitol‐based formulations, particularly at 10%, were highly effective in reducing anthracnose lesions on banana with 84.9% inhibition, and percent disease incidence reduction by up to 91.8% on naturally infected strawberry fruits. While moderate mannitol concentration maintained better yeast viability under osmotic stress, higher concentration impaired cell population over time. Morphological analysis revealed that extreme stress conditions led to reduced cell size, rougher textures and pseudohyphae formation, emphasising the impact of environmental stress on yeast cells. These findings underscore the robustness of M. caribbica YDP‐27 as a biocontrol agent, distinguishing it from other yeasts by its broad pathogen suppression, stress tolerance and formulation adaptability. The study provides novel insights into optimising yeast‐based biocontrol strategies, enhancing shelf life and efficacy against postharvest fungal pathogens.