Alleviation of salinity and metal stress using plant growth-promoting rhizobacteria isolated from semiarid Moroccan copper-mine soils.

Atika Madline,Ali Boularbah,Leila Benidire

doi:10.1007/s11356-021-15168-8

Abstract

Phytoremediation is an eco-friendly method for rehabilitation of mine tailing. Some heavy metals and salt-tolerant plant growth-promoting rhizobacteria (PGPR) could be beneficial in alleviating soil salinity and heavy metal stress during plant growth. The aim of this work is to select PGPR that could be used in phytoremediation process. Twenty-nine rhizobacteria are examined for their ability to grow at increasing concentrations of NaCl, Zn, Pb, Cu, and Cd. The results showed that seventeen rhizobacteria displayed high salinity and metal tolerance up to 100 g L-1 of NaCl, 5 mM of Cd, 9 mM of Pb, 10 mM of Zn, and 6 mM of Cu. Moreover, almost all tested bacteria maintained their PGP traits under 10% of NaCl and multi-metal stress. Based on seedling bioassay under metallic and salt stress, using Peganum harmala L. and Lactuca sativa L., beneficial effects of seed inoculation with bacterial consortia (Mesorhizobium tamadayense, Enterobacter xiangfangensis, Pseudomonas azotifigens, and Streptomyces caelestis) have been observed in terms of root and shoot elongation. Our results show that the stress-tolerant consortium used has a great potential to sustain plants establishment in heavily disturbed soils.

Highlights

Rapid population growth and increase in urbanization relies strongly on mining activities and industrial sector in order to produce commercial materials (Kabata-Pendias and Pendias, 2001)
Most of the tested rhizobacteria displayed a high level of multi-heavy metal resistance
The beneficial effects of osmotolerant plant growth promoting rhizobacteria (PGPR) strains on plants subjected to metal or salt stress was confirmed by an in vitro test

Summary

Introduction

Rapid population growth and increase in urbanization relies strongly on mining activities and industrial sector in order to produce commercial materials (Kabata-Pendias and Pendias, 2001) These activities involve several steps releasing different wastes, which may contain significant amounts of toxic contaminants that can pollute the air, soil, water and could affect negatively flora and fauna (El Khalil et al 2008; El Hamiani et al 2010). Due to their high toxicity and persistence within the environment, heavy metals are one of the major pollutants of the concern to human health (Adriano 2001). Several studies indicated that high level of heavy metals had various impacts on soil microbial composition and functional diversity (Boularbah et al 1992; Benidire et al 2016; Alam et al 2019; Lin et al 2019; Liu at al. 2019; Jiang et al 2019)

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