Investigating PGPR bacteria for their competence to protect hybrid maize from the factor drought stress

Drought and heat are severe environmental stresses that constantly affect plant growth and development. Maize (Zea mays L.) is known for its sensitivity to abiotic stresses, which often causes significant yield losses. With plant growth-promoting rhizobacteria (PGPR), the harmful effects of drought and heat stress on plants can be alleviated. The aim of the present study was to investigate the physiological traits of plants affected by drought stress in a treatment including four PGPR bacteria, two regimes of irrigation and two stages of phenophases, and the analysis of the influence of the individual factors and their combined effects, respectively. In addition, the investigations covered the testing of the nutrient acquisition ability and nutrient use efficiency, the plant growth stimulating effect of PGPR bacteria, and the analysis of the performance trials. The largest amount of soluble orthophosphate was produced by Pseudomonas putida (51.636 mu g/cm(3)). This is significantly more than the amount of phosphate solubilized by Bacillus pumilus (15.601 mu g/cm3), Pseudomonas fluorescens (14.817 mu g/cm3) and Bacillus megaterium (14.621 mu g/cm3). The germination vigour of the seedlings in the treatment with Pseudomonas putida was 55% higher, represented by the value of 15,237.125, in comparison with the control, with the value of 9792.188. The Pseudomonas putida treatment resulted in the most outstanding fresh/dry weight ratio (7.312) compared to the control (7.780), when the interaction between all factors was taken into account under stressed conditions at 50% female flowering stage. The highest dry matter content of the plants (18.344%) compared to the control (17.344%) was measured in the case of the Pseudomonas putida treatment during the milk stage of development under stressed conditions. In the field trial, the plants treated with KD2 (Bacillus pumilus and Pseudomonas putida) presented significantly higher results in the aspect of grain yield (6.278 t/ha) compared to the control (5.468 t/ha).