Rhizobacteria with ACC-Deaminase Activity Improve Nutrient Uptake, Chlorophyll Contents and Early Seedling Growth of Wheat under PEG-Induced Osmotic Stress

Drought stress is the leading constraint impairing the wheat growth across the globe. The 1-aminocyclopropane-1-carboxylate (ACC) deaminase producing plant growth promoting rhizobacteria (PGPRs) has the potential to mitigate the negative effects of drought stress on crops. This study was carried out to investigate the role of newly evolved ACC-deaminase containing PGPRs in improving the early wheat growth under polyethylene glycol (PEG) induced osmotic (drought) stress. Out of 45 strains isolated from wheat rhizosphere, 23 strains were found as drought-tolerant PGPRs, which were able to grow on 20% PEG containing Dworkin and Foster (DF) media. Among these 23, the 4 most effective ACC-deaminase producing PGPRs were selected, identified and characterized. Among these 4 strains, Leclercia adecarboxylata and Agrobacterium fabrum were newly reported and Bacillus amyloliquefaciens and Pseudomonas aeruginosa were earlier reported drought tolerant ACC-deaminase PGPRs. Wheat seeds inoculated with above mentioned strains of PGPRs and un-inoculated dry seeds were grown in hydroponic culture under three levels of PEG-induced drought stress i.e., 0 (-0.05 MPa), 10 (-0.23 MPa) and 20% (-0.78 MPa). PEG-induced osmotic stress, 20% PEG level was more severe, which decreased root and shoot lengths and dry weights, and seedling dry weight due to decreased chlorophyll contents and low uptake of nitrogen, phosphorus and potassium. However, seeds inoculation with PGPRs, especially newly reported strains L. adecarboxylata and A. fabrum, substantially improved seedling growth under osmotic stress due to elevated nutrients uptake and high chlorophyll contents. More wheat growth, under optimal and less than optimal conditions, subjected to L. adecarboxylata and A. fabrum application was linked with their higher ACC-deaminase and IAA production potential. In conclusion, newly reported drought tolerant ACC-deaminase containing PGPRs L. adecarboxylata and A. fabrum have the potential to improve early wheat growth under osmotic stress due to higher ACC-deaminase and IAA production potential. (C) 2019 Friends Science Publishers