The effect of yeast (Saccharomyces cerevisiae) application on fruit quality in apples

The increasing demand for sustainable and environmentally friendly production practices has intensified interest in microbial-based inputs as alternatives to synthetic agrochemicals in fruit cultivation. In this study, the effects of different doses of Saccharomyces cerevisiae on yield, pomological characteristics, physicochemical quality parameters, and antioxidant properties were investigated in two apple cultivars, Summer Red and Mondial Gala. The experiment was conducted during the 2024–2025 growing season under the ecological conditions of Eskişehir, Türkiye, using a randomized block design with four application doses (0, 5, 10, and 15 ppm). Results indicated that the response to S. cerevisiae applications was strongly dependent on cultivar and dose. In Summer Red, low-dose application (5ppm) significantly increased yield, total phenolic content, and ascorbic acid concentration, while higher doses showed limited or inconsistent effects on fruit quality traits. In contrast, Mondial Gala exhibited greater sensitivity to the treatments, with moderate doses (5 and 10 ppm) enhancing fruit weight and width, whereas higher doses tended to suppress certain quality attributes, particularly flavonoid and ascorbic acid contents. Color parameters and fruit firmness were generally less affected by the applications in both cultivars. Multivariate analyses (PCA and correlation analysis) revealed a clear separation between cultivar–dose combinations, highlighting distinct relationships between yield, fruit quality, and antioxidant parameters. Overall, the findings demonstrate that S. cerevisiae can be considered a promising biostimulant in apple cultivation; however, its effectiveness is highly genotype-specific and dose-dependent. Determination of optimal application doses tailored to individual cultivars is therefore essential to maximize both yield and fruit quality under sustainable production systems.