Zinc tolerant plant growth promoting bacteria alleviates phytotoxic effects of zinc on maize through zinc immobilization

Abstract

the increasing heavy metal contamination in agricultural soils has become a serious concern across the globe. The present study envisages developing microbial inoculant approach for agriculture in Zn contaminated soils. Potential zinc tolerant bacteria (ZTB) were isolated from zinc (Zn) contaminated soils of southern Rajasthan, India. Isolates were further screened based on their efficiency towards Zn tolerance and plant growth promoting activities. Four strains viz. ZTB15, ZTB24, ZTB28 and ZTB29 exhibited high degree of tolerance to Zn up to 62.5 mM. The Zn accumulation by these bacterial strains was also evidenced by AAS and SEM-EDS studies. Assessment of various plant growth promotion traits viz., iAA, GA 3 , nH 3 , Hcn, siderophores, Acc deaminase, phytase production and p, K, Si solubilization studies revealed that these ZTB strains may serve as an efficient plant growth promoter under in vitro conditions. Gluconic acid secreted by ZTB strains owing to mineral solubilization was therefore confirmed using high performance liquid chromatography. A pot experiment under Zn stress conditions was performed using maize (Zea mays) variety (FEM-2) as a test crop. Zn toxicity reduced various plant growth parameters; however, inoculation of ZTB strains alleviated the Zn toxicity and enhanced the plant growth parameters. The effects of Zn stress on antioxidant enzyme activities in maize under in vitro conditions were also investigated. An increase in superoxide dismutase, peroxidase, phenylalanine ammonia lyase, catalase and polyphenol oxidase activity was observed on inoculation of ZTB strains. Further, ZIP gene expression studies revealed high expression in the ZIP metal transporter genes which were declined in the ZTB treated maize plantlets. The findings from the present study revealed that ZtB could play an important role in bioremediation in Zn contaminated soils.

Ameliorative effect of indole-3-acetic acid- and siderophore-producing Leclercia adecarboxylata MO1 on cucumber plants under zinc stress

“…However, cucumber plants inoculated with the isolate MO1 showed a markedly increased chlorophyll content compared to that in zinc-treated non-inoculated control plants (Figure 2). These results are in agreement with previous findings (Joshi et al 2013;Islam et al 2014;Jain et al 2020), wherein the authors reported similar observations in maize and wheat seedlings under zinc stress.…”

“…Previously, several researchers have reported about different bacteria such as Serratia, Sphingomonas, and Rhizobium sp. in maize, sedum, and lentil, which increased the plant growth, biomass, and tolerance to zinc toxicity (Ahmad Wani et al 2008;Chen et al 2014;Jain et al 2020). Similarly, chlorophyll has a vital role in photosynthesis, and its synthesis was found to be inhibited under zinc stress.…”

Impacts of n‐acetyl cysteine on gibberellic acid‐induced hepatorenal dysfunction through modulation of pro‐inflammatory cytokines, antifibrotic and antioxidant activity

“…showed a substantial rise in nitric oxide expression in harmony with (Jain et al, 2020) in which they reported a high level of nitric oxide in rat administered gibberellic acid. NAC-treated group showed significant downregulation of TNFα, NFkB, and NOS concerning the gibberellic acid-treated group with significant upregulation of IL-10.…”

Phytomanagement of Metal(loid)-Contaminated Soils: Options, Efficiency and Value

“…Several authors reported enhanced activities of ROS-scavenging enzymes, e.g., superoxide dismutase (SOD), catalase (CAT), and ascorbate peroxidase (APx), when plants are exposed to high levels of TE (Ma et al, 2011b;Wang et al, 2011;Gupta et al, 2018;Saleem et al, 2018). The activity of these enzymes can be further improved by PGPB inoculation, which contributes to reduce oxidative damages in plants, as corroborated by the generalized decrease of malondialdehyde (MDA) contents often observed in inoculated plants (Wang et al, 2011;Gupta et al, 2018;Saleem et al, 2018;Jain et al, 2020).…”