In vitro rhizobia response and symbiosis process under aluminum stress

Abstract

Aluminum (Al) toxicity is a major problem affecting soil fertility, microbial diversity, and nutrient uptake of plants. Rhizobia response and legume interaction under Al conditions are still unknown; it is important to understand how to develop and improve legume cultivation under Al stress. In this study, rhizobia response was recorded under different Al concentrations. Al effect on rhizobial cells was characterized by combination with different two pH conditions. Symbiosis process was compared between α- and β-rhizobia inoculated onto soybean varieties. Rhizobial cell numbers was decreased as Al concentration increased. However, induced Al tolerance considerably depended on rhizobia types and their origins. Accordingly, organic acid results were in correlation with growth rate and cell density which suggested that citric acid might be a positive selective force for Al tolerance and plant interaction on rhizobia. Al toxicity delayed and interrupted the plant-rhizobia interaction and the effect was more pronounced under acidic conditions. Burkholderia fungorum VTr35 significantly improved plant growth under acid-Al stress in combination with all soybean varieties. Moreover, plant genotype was an important factor to establish an effective nodulation and nitrogen fixation under Al stress. Additionally, tolerant rhizobia could be applied as an inoculant on stressful agroecosystems. Furthermore, metabolic pathways have still been unknown under Al stress.

Rhizobial–Host Interactions and Symbiotic Nitrogen Fixation in Legume Crops Toward Agriculture Sustainability

“…An excessive level of Al under low pH conditions reduced nitrogenase activity by as much as 50% in addition to biochemical changes in the nodules during the Phaseolus vulgaris-R. tropici CIAT899 symbiosis (Mendoza-Soto et al, 2015). The prominent mechanisms of Al toxicity mitigation in rhizobia include induction of efflux pumps, reduction in Al uptake through synthesis of siderophores, production of exopolysaccharides, and synthesis of citric acid (Artigas Ramírez et al, 2018;Jaiswal et al, 2018). Heavy metal contamination of the soil has negative effects on plant growth and development as well as symbiotic activity (DalCorso, 2012).…”

Are Nanoparticles a Threat to Mycorrhizal and Rhizobial Symbioses? A Critical Review

“…However, rhizobia possess the biochemical and ecological capacity to decrease the risks associated with metals, metalloids, and organic pollutants in contaminated soils (Teng et al, 2015). For instance, the acidic-Al tolerant Burkholderia fungorum VTr35 strain was shown to induce tolerance to soybean plants against acid-Al stress conditions (Ramirez et al, 2018). Furthermore, rhizobia were shown to confer tolerance to host plants against heavy metals and oxidative stress through production of hydrogen (H 2 ), which is a by-product of the symbiotic N 2 fixation process and possess novel bioactive properties (Cui et al, 2013; Jin et al, 2013).…”

“…Plants from Fabaceae family enter into a symbiotic relationship with soil bacteria (including Rhizobium , Bradyrhizobium , Sinorhizobium , and Burkholderia) , which converts the atmospheric N 2 to ammonia, referred to as rhizobial symbiosis (Oldroyd et al, 2011). Rhizobial symbioses make significant contributions to N nutrition of Fabaceae (the third largest plant family), legume crops and non-legume crops grown in rotation, and tolerance against environmental stresses such as heavy metals, organic pollutants and acidity (Crews and Peoples, 2004; Teng et al, 2015; Ramirez et al, 2018). At the symbiotic interface, roots form nodules to accommodate N 2 -fixing rhizobia.…”

The Cell Membrane of a Novel Rhizobium phaseoli Strain Is the Crucial Target for Aluminium Toxicity and Tolerance

“…Anthropogenic activities and, in particular, mineral leaching in the tropical soils have increased soil acidification up to the pHs between 5.5 and 4.6, and in extreme cases even below 4.5 [ 12 ]. Consequently, insoluble Al salts dissociate [ 13 ] in agricultural areas [ 14 ]. Plants counteract increasing Al stress in the soil by exuding organic acids and protons, immobilizing Al 3+ by secretion of mucilage, sequestrating the ion in the vacuole, or secreting it from the root cells into the surrounding rhizosphere.…”