Drought-Tolerant Pseudomonas spp. Improve the Growth Performance of Finger Millet (Eleusine coracana (L.) Gaertn.) Under Non-Stressed and Drought-Stressed Conditions

Abstract

Application of plant growth-promoting bacteria (PGPB) is an environmentally sustainable option to reduce the effects of abiotic and biotic stresses on plant growth and productivity. Three 1-aminocyclopropane-1-carboxylic acid (ACC) deaminase-producing drought-tolerant bacteria were isolated from a rain-fed agriculture field in the Central Himalaya of Kumaun region, Uttarakhand, India and evaluated for their efficiency in improving finger millet (Eleusine coracana (L.) Gaertn.) plant growth under non-stressed and drought-stressed conditions. These bacteria withstood a substrate metric potential of −1.0 MPa (30% polyethylene glycol 8000) and therefore were considered drought-tolerant. These strains were identified as Pseudomonas spp. by fatty acid methyl ester analysis and 16S rRNA gene sequencing. The ACC deaminase activity of these strains was characterized at the biochemical level, and the presence of acdS gene, the structural gene for ACC deaminase, was confirmed by the polymerase chain reaction. Two sets of pot trials in glass house were set up, one for normal (non-stressed) and the other for drought-stressed conditions. After 5 weeks, one set of plants was subjected to drought stress for 5 d, while the other set continued to be watered. The same growth parameters were recorded for both sets of plants after 40 d of plant growth. The results of pot trials showed that treatments inoculated with ACC deaminase-producing bacterial strains significantly improved the growth performance of finger millet plants and foliar nutrient content as compared to uninoculated treatments under both non-stressed and drought-stressed conditions. In addition, a significant increase in antioxidant activity was observed, wherein bacterial stain inoculation improved plant fitness by protecting it from oxidative damage induced by drought.