Plant growth promoting rhizobacteria induced metal and salt stress tolerance in Brassica juncea through ion homeostasis

Umar Daraz; Iftikhar Ahmad; Qu-Sheng Li; Bo Zhu; Muhammad Farhan Saeed; Yang Li; Jianguo Ma; Xiao-Bo Wang

doi:10.1016/j.ecoenv.2023.115657

Plant growth promoting rhizobacteria induced metal and salt stress tolerance in Brassica juncea through ion homeostasis

Ecotoxicol Environ Saf. 2023 Nov 15:267:115657. doi: 10.1016/j.ecoenv.2023.115657. Epub 2023 Nov 2.

Authors

Umar Daraz¹, Iftikhar Ahmad², Qu-Sheng Li³, Bo Zhu⁴, Muhammad Farhan Saeed⁵, Yang Li⁶, Jianguo Ma¹, Xiao-Bo Wang⁷

Affiliations

¹ State Key Laboratory of Herbage Improvement and Grassland Agro-ecosystems, Center for Grassland Microbiome, and College of Pastoral Agriculture Science and Technology, Lanzhou University, Lanzhou 730000, China.
² Department of Environmental Sciences, COMSATS University Islamabad, Vehari Campus, Vehari 61100, Pakistan; Shanghai Yangtze River Delta Eco-Environmental Change and Management Observation and Research Station, Ministry of Science and Technology, Ministry of Education, Shanghai Urban Forest Ecosystem Research Station, National Forestry and Grassland Administration, Shanghai Cooperative Innovation Center for Modern Seed Industry, School of Agriculture and Biology, Shanghai Jiao Tong University, Shanghai 200240, China. Electronic address: iftikharahmad@cuivehari.edu.pk.
³ Guangdong Key Laboratory of Environmental Pollution and Health, School of Environment, Jinan University, Guangzhou 510632, China.
⁴ Shanghai Yangtze River Delta Eco-Environmental Change and Management Observation and Research Station, Ministry of Science and Technology, Ministry of Education, Shanghai Urban Forest Ecosystem Research Station, National Forestry and Grassland Administration, Shanghai Cooperative Innovation Center for Modern Seed Industry, School of Agriculture and Biology, Shanghai Jiao Tong University, Shanghai 200240, China.
⁵ Department of Environmental Sciences, COMSATS University Islamabad, Vehari Campus, Vehari 61100, Pakistan.
⁶ State Key Laboratory of Mining Response and Disaster Prevention and Control in Deep Coal Mines, Anhui University of Science & Technology, Huainan, Anhui Province, China.
⁷ State Key Laboratory of Herbage Improvement and Grassland Agro-ecosystems, Center for Grassland Microbiome, and College of Pastoral Agriculture Science and Technology, Lanzhou University, Lanzhou 730000, China. Electronic address: wangxiaobo@lzu.edu.cn.

PMID: 37924800
DOI: 10.1016/j.ecoenv.2023.115657

Abstract

Soil heavy metal contamination and salinity constitute a major environmental problem worldwide. The affected area and impact of these problems are increasing day by day; therefore, it is imperative to restore their potential using environmentally friendly technology. Plant growth-promoting rhizobacteria (PGPR) provides a better option in this context. Thirty-seven bacteria were isolated from the rhizosphere of maize cultivated in metal- and salt-affected soils. Some selected bacterial strains grew well under a wide range of pH (4-10), salt (5-50 g/L), and Cd (50-1000 mg/L) stress. Three bacterial strains, Exiguobacterium aestuarii (UM1), Bacillus cereus (UM8), and Bacillus megaterium (UM35), were selected because of their robust growth and high tolerance to both stress conditions. The bacterial strains UM1, UM8, and UM35 showed P-solubilization, whereas UM8 and UM35 exhibited 1-aminocyclopropane-1-carboxylate deaminase activity and indole acetic acid (IAA) production, respectively. The bacterial strains were inoculated on Brassica juncea plants cultivated in Cd and salt-affected soils due to the above PGP activities and stress tolerance. Plants inoculated with the bacterial strains B. cereus and B. megaterium significantly (p < 0.05) increased shoot fresh weight (17 ± 1.17-29 ± 0.88 g/plant), shoot dry weight (2.50 ± 0.03-4.40 ± 0.32 g/plant), root fresh weight (7.30 ± 0.58-13.30 ± 0.58 g/plant), root dry weight (0.80 ± 0.04-2.00 ± 0.01 g/plant), and shoot K contents (62.76 ± 1.80-105.40 ± 1.15 mg/kg dwt) in normal and stressful conditions. The bacterial strain B. megaterium significantly (p < 0.05) decreased shoot Na⁺ and Cd⁺⁺ uptake in single and dual stress conditions. Both bacterial strains, E. aestuarii and B. cereus, efficiently reduced Cd⁺⁺ translocation and bioaccumulation in the shoot. Bacterial inoculation improved the uptake of K⁺ and Ca⁺⁺, while restricted Na⁺ and Cd⁺⁺ in B. juncea shoots indicated their potential to mitigate the dual stresses of salt and Cd in B. juncea through ion homeostasis.

Keywords: Brassica juncea; Metal stress; Nutrient availability; PGPR; Salt-stress.

MeSH terms

Bacillus megaterium*
Cadmium / toxicity
Homeostasis
Mustard Plant*
Plant Roots
Plants
Salt Tolerance
Soil
Soil Microbiology

Substances

Cadmium
Soil