Plant Growth-Promoting Yeasts from Vitis vinifera subsp. sylvestris 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 Vitis vinifera subsp. sylvestris and performed systematic in vitro 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 Nicotiana tabacum; ten increased biomass, leaf area, and root traits versus the control. The standout strains were Wickerhamomyces anomalus C(H5.1), Metschnikowia pulcherrima B(B5) and C(A11.2), Pichia kudriavzevii C(A7), and Yarrowia lipolytica 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.