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 (, , and some yeast) in 10 CFU/mL concentrations for seed priming and later in the same concentration for seedling spraying. A total of 70 g/m CaCO or 100 g/m CaCl was added to the soil before sowing the seeds. Almost all tested treatments improved plant growth and positively affected prolonged drought resistance in winter wheat. , in combination with calcium salts, had the greatest effect on maintaining the relative leaf water content (RWC). The proline, malondialdehyde (MDA), and HO tests proved the significant positive impact of the treatments on the plant's response at the biochemical level, with growth parameters close to those of irrigated plants, for example, the ones treated with alone or with Ca salts had the lowest HO content, 0.86-0.96 μmol g FW, compared to 3.85 μmol g FW for the Control, along with lower levels of drought-induced gene expression. All the presented results show statistically significant differences ( < 0.05). 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.