Phyllosphere Yeast Meyerozyma caribbica YDP-27: Effective Biocontrol Against Post-Harvest Pathogens With Stress Resilience

Abstract

Post-harvest losses caused by the fungal pathogens constitute a serious issue, especially during the storage and transportation of perishable fruits and vegetables. This study assessed the potential of the phyllosphere yeast Meyerozyma caribbica YDP-27 in supressing post-harvest diseases caused by six fungal pathogens viz., Colletotrichum musae, C. capsici, C. gloeosporioides, Alternaria alternata, Curvularia alcornii and Pestalotiopsis sp. The yeast exhibited moderate biocontrol potential in vitro, with an average mycelial growth inhibition of 31.11% after 7 days of dual culture across all tested pathogens. The study also examined how environmental stresses, such as elevated temperature, oxidative stress and osmotic stress impacted the yeast viability and morphology. Results showed that high temperatures (40°C and 42°C) and elevated hydrogen peroxide concentration significantly reduced yeast populations. The addition of 5% sorbitol and ascorbic acid enhanced the yeast's oxidative stress tolerance and viability. Sorbitol-based YDP-27 formulations, particularly at 15%, were highly effective in reducing anthracnose lesions on banana and mango fruits, achieving up to 100% inhibition. While moderate sorbitol concentration maintained better yeast viability under osmotic stress, higher concentration impaired cell populations over time. Morphological analysis revealed that extreme stress conditions led to reduced cell size, rougher textures and the formation of pseudohyphae. These findings underscore the potential of M. caribbica YDP-27 as a biocontrol agent, with specific additives significantly enhancing its performance under stress, thereby improving its shelf life and effectiveness against post-harvest pathogens.