The emerging roles of yeasts as plant growth promoters: mechanisms, benefits, and agricultural applications.

The increasing global demand for sustainable agricultural practices has intensified the search for eco-friendly alternatives to chemical fertilizers and pesticides. Plant growth-promoting yeasts (PGPYs) have garnered significant attention for their ability to enhance crop productivity, stress resilience and soil health. While PGPR and PGPF have been extensively studied in this context, yeast, particularly non-pathogenic strains, are emerging as promising yet underexplored candidates. Plant growth-promoting yeasts (PGPYs) are a diverse group of unicellular fungi that can colonize the rhizosphere, phyllosphere, and even internal plant tissues. This review summarizes the current knowledge on the mechanisms by which PGPYs promote plant growth, including nutrient acquisition, phytohormone production, antimicrobial compounds, stress tolerance, and disease suppression. Furthermore, the ecological roles of PGPYs in various plant–microbe systems are discussed, highlighting their applications in different agroecosystems. They are generally more resilient to environmental stressors, have a longer shelf life in formulations, and are easier to mass-produce compared to other PGPMs. This review also addresses the challenges in utilizing PGPYs as biofertilizers and biocontrol agents. It suggests future research directions to enhance the efficacy and applications of these agents as plant growth promoters for sustainable agricultural practices.