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Soil deterioration has led to problems with the nutrition of the world’s population. As one of the most serious stressors, soil salinization has a negative effect on the quantity and quality of agricultural production, drawing attention to the need for environmentally friendly technologies to overcome the adverse effects. The use of plant-growth-promoting bacteria (PGPB) can be a key factor in reducing salinity stress in plants as they are already introduced in practice. Plants having halotolerant PGPB in their root surroundings improve in diverse morphological, physiological, and biochemical aspects due to their multiple plant-growth-promoting traits. These beneficial effects are related to the excretion of bacterial phytohormones and modulation of their expression, improvement of the availability of soil nutrients, and the release of organic compounds that modify plant rhizosphere and function as signaling molecules, thus contributing to the plant’s salinity tolerance. This review aims to elucidate mechanisms by which PGPB are able to increase plant tolerance under soil salinity.

Contamination of agricultural soils with trace elements (TEs) through municipal and industrial wastes, atmospheric deposition and fertilisers is a matter of great global concern. Since TE accumulation in edible plant parts depends on soil characteristics, plant genotype and agricultural practices, those soiland plant-specific options that restrict the entry of harmful TEs into the food chain to protect human and animal health are reviewed. Soil options such as in situ stabilisation of TEs in soils, changes in physicochemical parameters, fertiliser management, element interactions and agronomic practices reduce TE uptake by food crops. Furthermore, phytoremediation and solubilisation as alternative techniques to reduce TE concentrations in soils are also discussed. Among plant options, selection of species and cultivars, metabolic processes and microbial transformations in the rhizosphere can potentially affect TE uptake and distribution in plants. For this purpose, genetic variations are exploited to select cultivars with low uptake potential, especially low-cadmium accumulator wheat and rice cultivars. The microbial reduction of elements and transformations in the rhizosphere are other key players in the cycling of TEs that may offer the basis for a wide range of innovative biotechnological processes. It is thus concluded that appropriate combination of soil-and plant-specific options can minimise TE transfer to the food chain.

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BACKGROUND Heavy metal contamination results in oxidative stress to plants and leads to decreased plant growth and development. Affected plants cannot be efficiently used in phytoremediation studies and their potential may be significantly reduced. In many cases, bioaugmentation with plant growth‐promoting bacteria is used as a strategy to alleviate this stress condition. RESULTS Isolates were found to possess 1‐aminocyclopropane‐1‐carboxylate (ACC) deaminase, to produce indole‐3‐acetic acid (IAA) siderophores and to solubilize phosphates, while identification revealed that the isolates belonged to the genera Pseudomonas and Bacillus. Out of the 17 isolates, ten were found to possess ACC deaminase activity, producing 1–3.2 μmol mg−1 h−1 of α‐ketobutyrate and siderophores of catechol and hydroxamate type. A higher quantity of IAA was observed in the case of isolate SGPI 41 (65 μg mL−1). In addition, the inoculation of consortia of isolates led to decreased accumulation of Cd, Pb and Zn in the whole plant but at the same time increased the plant biomass by up to 100% compared with the un‐inoculated control. CONCLUSIONS The use of beneficial bacteria possessing plant growth‐promoting traits is a very useful approach to alleviating heavy metal stress to plants and can be successfully applied in phytoremediation strategies. © 2019 Society of Chemical Industry

The application of plant beneficial microorganisms has been widely accepted as an efficient alternative to chemical fertilizers and pesticides. Isolation and selection of efficient microorganisms, their characterization and testing in soil-plant systems are well studied. However, the production stage and formulation of the final products are not in the focus of the research, which affects the achievement of stable and consistent results in the field. Recent analysis of the field of plant beneficial microorganisms suggests a more integrated view on soil inoculants with a special emphasis on the inoculant production process, including fermentation, formulation, processes, and additives. This mini-review describes the different groups of fermentation processes and their characteristics, bearing in mind different factors, both nutritional and operational, which affect the biomass/spores yield and microbial metabolite activity. The characteristics of the final products of fermentation process optimization strategies determine further steps of development of the microbial inoculants. Submerged liquid and solid-state fermentation processes, fed-batch operations, immobilized cell systems, and production of arbuscular mycorrhiza are presented and their advantages and disadvantages are discussed. Recommendations for further development of the fermentation strategies for biofertilizer production are also considered.