Halotolerant potassium solubilizing plant growth promoting rhizobacteria may improve potassium availability under saline
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Halotolerant potassium solubilizing plant growth promoting rhizobacteria may improve potassium availability under saline conditions Muhammad Ashfaq & Hasnuri Mat Hassan & Amir Hamzah Ahmad Ghazali & Maqshoof Ahmad
Received: 28 May 2020 / Accepted: 30 September 2020 # Springer Nature Switzerland AG 2020
Abstract Environmental change is one of the primary issues faced by the farming community. Low rainfall and high temperature in arid and semiarid regions lead to the development of secondary salinisation, thus making the problem more severe. Under saline conditions, sodium is the most crucial cation that competes with potassium (K) and adversely affects plant metabolism by inhibiting plant enzymatic activities. Potassiumsolubilising bacteria (KSB) play a vital role in solubilising fixed potassium and making it accessible to plants. In the current study, 42 KSB strains were isolated from paddy rhizosphere soil grown under saltaffected conditions. The plant-growth-promoting (PGP) properties of these rhizobacteria were also evaluated. Thirteen KSB strains, positive for all tested PGP traits, were evaluated for potassium solubilisation under sodium stress, namely, 0%, 3%, 5% and 7% NaCl stress. The five best strains (Acinetobacter pittii strain L1/4, A. pittii strain L3/3, Rhizobium pusense strain L3/4, Cupriavidus oxalaticus strain L4/12 and Ochrobactrum ciceri strain L5/1) based on the K-solubilising potential were identified by amplification, sequencing and bioinformatic analysis of the 16S rDNA sequences. The M. Ashfaq (*) : H. M. Hassan (*) : A. H. A. Ghazali School of Biological Sciences, Universiti Sains Malaysia, 11800 USM, Pulau Pinang, Malaysia e-mail: [email protected] e-mail: [email protected] M. Ahmad Department of Soil Science, The Islamia University of Bahawalpur, Bahawalpur 63100, Pakistan
maximum potassium solubilisation was measured at 30 °C and pH 7 with glucose as carbon source. The application of these KSB strains significantly improved the shoot length, fresh weight, dry weight and chlorophyll contents of paddy plants grown under saline conditions. Hence, these strains could be halotolerant KSB bioinoculants that can be used to protect plants against salt stress. Keywords Ionic balance . Potassium-solubilising bacteria . Nutrient solubilisation . Saline soils
Introduction Since the beginning of agriculture, the demand to improve crop yield has been a problem that needs to be addressed in order to meet the food requirement of a growing population. Estimates show that by 2050, the grain yield of major cereal crops should be increased by at least 50% in order to fulfil the food requirements of the world population (Godfray et al. 2010). Numerous abiotic factors such as temperature, salinity, soil pH, drought, agrochemicals and heavy metal contamination affect agricultural produce (Ahmad 2014). Amongst them, soil salinity is a significantly high-risk factor for agricultural production (Shrivastava and Kumar 2015). Recently, an increase in the salinisation rate of fertile land has resulted in food
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