Soil yeasts promoting plant growth: benefits for the development of common wheat and white mustard

A large number of soil microorganisms are characterized as plant growth promoting, but there seems to be a lack of comprehensive knowledge regarding plant growth promoting soil yeasts. The aim of the experiment was to analyse the properties of three yeast species: Schwanniomyces occidentalis BK0302D, Cyberlindnera saturnus CK2404I and Candida tropicalis 2TD2912B, important for plant growth (ammonium sulphate transformation, phosphorus, potassium and zinc dissolution), and to evaluate the effect of yeast on the growth of common wheat and white mustard seedlings after seeds’ inoculation. Common wheat and white mustard seeds were inoculated with the selected yeasts. The final measurements showed that the highest amount of nitrate (10.40 μg mL-1 NO3 −) was produced by C. saturnus CK2404I, while S. occidentalis BK0302D solubilized the largest amount of phosphorus (63.70 μg mL-1 P). All three strains are marked as potassium and zinc solubilizers with both acid and alkaline phosphatase activity. This is the first report on S. occidentalis and C. tropicalis ability to solubilize insoluble potassium and zinc, and C. saturnus ability to solubilize insoluble phosphorus, potassium and zinc. Also, C. tropicalis 2TD2912B exhibited high antagonistic activity (66% growth inhibition) toward Botrytis cinerea. In vivo trial was conducted in a low-nutrient substrate, and S. occidentalis BK0302D was found to have the most considerable influence on common wheat biomass production (34% increase). White mustard inoculation with C. saturnus CK2404I resulted in a 4-fold higher biomass production, while S. occidentalis BK0302D induced a 2-fold increase. The presented results confirmed the multi-functional plant growth promoting characteristics of the tested yeasts and their potential for broad application from conventional agriculture on low-nutrient soils to revegetation of disturbed substrates.