Physiological, Biochemical, and Genetic Reactions of Winter Wheat to Drought Under the Influence of Plant Growth Promoting Microorganisms and Calcium

Improving wheat drought stress tolerance is a critical and challenging task, and more research is necessary since many parts of the world depend on this crop for food and feed. Our current work is focused on the influence of probiotic microorganisms in combination with calcium salts on the physiological and biochemical metabolic pathways that wheat uses when exposed to drought stress and on the analysis of gene expression levels that contribute to wheat drought tolerance. The research was conducted in the laboratory under controlled conditions, simulating a prolonged drought. Seedlings were treated with different microorganisms (Bacillus subtilis, Lactobacillus paracasei, and some yeast) in 105 CFU/ml concentrations for seed priming and later in the same concentration for seedling spraying. 70 g/m2 CaCO3 or 100 g/m2 CaCl2 was added to the soil before the sowing seeds. Almost all tested treatments improved plant growth and positively affected prolonged drought resistance in winter wheat. Bacillus subtilis, in combination with calcium salts, had the greatest effect on maintaining the relative leaf water content (RWC). Proline, MDA, and H2O2 tests proved a significant positive impact of the treatments on the plant's response at the biochemical level and growth parameters close to those of irrigated plants, along with lower levels of drought-induced gene expression. This study showed that tested microorganisms in combination with calcium salts can activate plants' defense reactions in response to drought. The practical significance of this study is that these ecological measures can be useful under field conditions.