<em>Debaryomyces hansenii</em> as an Inducing Agent of Growth, Development and Production in Rice Plants (<em>Oryza sativa</em> L.) Grown in Calcareous Soil

Calcareous soils, characterized by high pH and calcium carbonate content, often limit the availability of essential nutrients for crops such as rice (Oryza sativa L.), reducing yield and nutritional quality. In this study, we evaluated the effect of the halotolerant yeast Debaryomyces hansenii (Dh) on the growth, nutrient uptake, and phosphorus acquisition mechanisms of rice plants cultivated in calcareous soil under controlled greenhouse conditions. Plants inoculated with Dh, particularly via root immersion, exhibited significantly higher SPAD chlorophyll index, plant height, dry matter content, and grain yield compared to controls. Foliar concentrations of Cu, Fe, Zn, and Mn also increased under certain conditions, suggesting improved micronutrient acquisition. Although phosphorus levels in leaves were not significantly enhanced, Dh stimulated acid phosphatase activity in both P-sufficient and P-deficient treatments. At the molecular level, Dh upregulated the expression of acid phosphatase genes (OsPAP3, OsPAP9) and a phosphate transporter gene (OsPTH1;6), confirming its influence on P-related physiological responses. These findings demonstrate that D. hansenii functions as a plant growth-promoting yeast (PGPY) and may serve as a promising biofertilizer for improving rice productivity and nutrient efficiency in calcareous soils, contributing to sustainable agricultural practices in challenging edaphic environments.