Abstract
The demand for agricultural crops continues to escalate with an increasing population. To meet this demand, marginal land can be used as a sustainable source for increased plant productivity. However, moisture stress not only affects crop growth and productivity but also induces plants’ susceptibility to various diseases. The positive role of plant growth hormone, salicylic acid (SA), on the defence systems of plants has been well documented. With this in mind, a combination of plant growth promoting rhizobacteria (PGPR) and SA was used to evaluate its performance on wheat grown under rainfed conditions (average moisture 10–14%). The selected bacterial strains were characterized for proline production, indole-3-acetic acid (IAA), hydrogen cyanide (HCN), ammonia (NH3), and exopolysaccharides (EPS). Wheat seeds of two genotypes, Inqilab-91 (drought tolerant) and Shahkar-2013 (drought sensitive), which differed in terms of their sensitivity to drought stress, were soaked for three hours prior to sowing in 24-hour old cultures of the bacterial strains Planomicrobium chinense strain P1 (accession no. MF616408) and Bacillus cereus strain P2 (accession no. MF616406). SA was applied (150 mg/L), as a foliar spray on one-month-old wheat seedlings. A significant reduction in the physiological parameters was noted in the plants grown in rainfed conditions but the PGPR and SA treatment effectively ameliorated the adverse effects of moisture stress. The wheat plants treated with PGPR and SA showed significant increases in leaf protein and sugar contents and maintained higher chlorophyll content, chlorophyll fluorescence (fv/fm) and performance index (PI) under rainfed conditions. Leaf proline content, lipid peroxidation, and antioxidant enzyme activity were higher in the non-inoculated plants grown in rainfed conditions but significantly reduced in the inoculated plants of both genotypes. Integrative use of a combination of PGPR strains and SA appears to be a promising and eco-friendly strategy for reducing moisture stress in plants.
Highlights
The current scenario of climate change has resulted in global warming coupled with infrequent precipitation, subsequently increasing the demand for irrigation [1]
The two selected plant growth promoting rhizobacteria (PGPR) isolates were checked for the production of NH3 and hydrogen cyanide (HCN) and found that both of them were positive for NH3 and HCN production
The chemical composition of PGPR-induced EPS shows that the EPS produced by P. chinense had a higher percentage of sugar and protein (i.e. 97% and 98% respectively) as compared to control
Summary
The current scenario of climate change has resulted in global warming coupled with infrequent precipitation, subsequently increasing the demand for irrigation [1]. Rainfed soils are incapable of moving water from deeper layers of soils through capillary action. Plant roots produce an array of organic compounds that are an efficient source of carbon inside the soil [7,8]. These compounds are secreted from the roots as exudates; they attract soil microbes, including PGPR [9, 10]. Rhizobacteria maintain the water budget of plants under rainfed conditions by improving the growth of the root system [11]. Siderophores, biofilm and plant hormones which influence plant physiological processes [21]
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