Alleviation of Drought Stress and Plant Growth Promotion by Pseudomonas libanensis EU-LWNA-33, a Drought-Adaptive Phosphorus-Solubilizing Bacterium

Abstract

Drought is a very common abiotic stress worldwide in arid and semiarid areas. It decreases the growth and yield of the crops. Due to drought stress, there is insufficient intake of the nutrients, the low rate of photosynthesis and limited supply of water in plants. Inoculating crops with plant growth-promoting rhizobacteria (PGPR) mitigates the deleterious effects of stress by promoting beneficial effects such as helping them in the acquisition of less available nutrients, increasing the levels of plant growth regulators, improving the physiological health of the plants. In the present study, drought-tolerant phosphorus-solubilizing rhizobacteria with multifunctional plant growth-promoting attributes were isolated from different cereal crops grown in the Divine Valley of Baru Sahib, Himachal Pradesh, using a different nutrient combination. A total of 86 bacteria were isolated from different growth media. All 86 could tolerate 5% PEG, and 19, 6 and 6 isolates could tolerate 6%, 7% and 8% PEG-8000, respectively. Among 86, 48 drought-adapted and P-solubilizing strains were selected and screened for diverse PGP attributes such as solubilization of potassium and zinc, production of siderophores, hydrogen cyanide, ammonia and 1-aminocyclopropane-1-carboxylate deaminase. The efficient drought-adaptive P-solubilizing strain was used for seed germination and plant growth-promoting ability in different pot assays under laboratory and greenhouse conditions at different water regimes. The strain EU-LWNA-33 positively influencing the growth parameters and physiological parameters was identified using 16 S rRNA gene sequencing as Pseudomonas libanensis. To our knowledge, this is the first report for P. libanensis EU-LWNA-33 to solubilize a considerable amount of P under the water-deficient conditions. The use of stress-adaptive and P-solubilizing PGPR provides significant promise to overcome the challenges of sustainable agriculture in stressed environmental conditions.