Assessing the Plant Growth Promoting and Arsenic Tolerance Potential of Bradyrhizobium japonicum CB1809
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Assessing the Plant Growth Promoting and Arsenic Tolerance Potential of Bradyrhizobium japonicum CB1809 Md Ferdous Seraj1,2 Tania Rahman3 Ann C. Lawrie4 Suzie M. Reichman ●
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Received: 8 January 2020 / Accepted: 21 August 2020 © Springer Science+Business Media, LLC, part of Springer Nature 2020
Abstract Accumulation of heavy metals in soil is of concern to the agricultural production sector, because of the potential threat to food quality and quantity. Inoculation with plant growth-promoting bacteria (PGPR) has previously been shown to alleviate heavy metal stress but the mechanisms are unclear. Potential mechanisms by which inoculation with Bradyrhizobium japonicum CB1809 affected the legume soybean (Glycine max cv. Zeus) and the non-legume sunflower (Helianthus annus cv. Hyoleic 41) were investigated in solution culture under 5 μM As stress. Adding As resulted in As tissue concentrations of up to 5 mg kg−1 (shoots) and 250 mg kg−1 (roots) in both species but did not reduce shoot or root biomass. Inoculation increased root biomass but only in the legume (soybean) and only with As. Inoculation resulted in large (up to 100%) increases in siderophore concentration but relatively small changes (±10–15%) in auxin concentration in the rhizosphere. However, the increase in siderophore concentration in the rhizosphere did not result in the expected increases in tissue N or Fe, especially in soybean, suggesting that their function was different. In conclusion, siderophores and auxins may be some of the mechanisms by which both soybean and sunflower maintained plant growth in As-contaminated media. Keywords Plant growth-promoting rhizobacteria (PGPR) Arsenic Bioremediation Soybean Sunflower Bradyrhizobium japonicum ●
Introduction Contamination of soil by the metalloid arsenic is a worldwide problem resulting from its widespread and versatile uses in industry. The major form of arsenic in soil is As(V), which is much less toxic than As(III) (Abbas et al. 2018). Arsenic contamination of existing soils is difficult to bioremediate (Malik et al. 2009). Mechanical solutions
* Suzie M. Reichman [email protected] 1
School of Engineering, RMIT University, Melbourne, VIC, Australia
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Department of Environmental Science and Management, North South University, Dhaka, Bangladesh
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Department of Biochemistry and Molecular Biology, University of Dhaka, Dhaka, Bangladesh
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School of Science, RMIT University, Bundoora, VIC, Australia
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Centre for Anthropogenic Pollution Impact and Management, School of BioSciences, University of Melbourne, Parkville, VIC, Australia
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(removal and burial off-site) are expensive (Australian State of Environment Committee, Australia 2001) and only remove the problem elsewhere, for it possibly to reappear as contamination of waterways and the food chain (Madejón et al. 2010). Interest in alternative solutions to As contamination has focused on plant-based remediation of As-containing soils by utilising rhizosphere bacteria (Hinsinger et
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