Plant Growth-Promoting Yeasts from <i>Vitis vinifera</i> subsp. <i>sylvestris</i> as Promising Bioinoculants for Sustainable Crop Production

Plant growth-promoting yeasts are promising bioinoculants for low-input agriculture, yet their application remains underexplored. We isolated 25 epiphytic strains from <i>Vitis vinifera</i> subsp. <i>sylvestris</i> and performed systematic <i>in vitro</i> biochemical profiling of plant growth promoting (PGP) traits. All produced indole-3-acetic acid (IAA); 80% synthesized under L-tryptophan-free conditions, indicating tryptophan-independent routes. ACC deaminase, siderophores, ammonia release, catalase, and biofilm were widespread, whereas nutrient solubilization (P, K, Zn), polyamines, and hydrolases (proteases, chitinases, β-1,3-glucanases, lipases, esterases) were strain-dependent, guiding evidence-based selection. Twelve representatives were evaluated in greenhouse with <i>Nicotiana tabacum</i>; ten increased biomass, leaf area, and root traits <i>versus</i> the control. The standout strains were <i>Wickerhamomyces anomalus</i> C(H5.1), <i>Metschnikowia pulcherrima</i> B(B5) and C(A11.2), <i>Pichia kudriavzevii</i> C(A7), and <i>Yarrowia lipolytica</i> B(H3.1.1), each displaying broad functional repertoires and consistent greenhouse performance. Growth promotion occurred without detectable shifts in bulk soil chemistry, supporting native epiphytic yeasts as multifunctional, soil safe bioinoculant candidates.