Effects of Rhizobium leguminosarum Thy2 on the Growth and Tolerance to Cadmium Stress of Wheat Plants

Abstract

Cadmium (Cd) stress is an obstacle for crop production, quality crops, and sustainable agriculture. An important role is played by the application of eco-friendly approaches to improve plant growth and stress tolerance. In the current study, a pre-sowing seed treatment with Rhizobium leguminosarum strains, isolated from the leguminous plants Phaseolus vulgaris (strain Pvu5), Vicia sylvatica (strain VSy12), Trifolium hybridium (strain Thy2), and T. pratense (strain TPr4), demonstrated different effects on wheat (Triticum aestivum L.) plant growth under normal conditions. Among all tested strains, Thy2 significantly increased seed germination, seedling length, fresh and dry biomass, and leaf chlorophyll (Chl) content. Further analysis showed that Thy2 was capable of producing indole-3-acetic acid and siderophores and fixing nitrogen. Under Cd stress, Thy2 reduced the negative effect of Cd on wheat growth and photosynthesis and had a protective effect on the antioxidant system. This was expressed in the additional accumulation of glutathione and proline and the activation of glutathione reductase. In addition, Thy2 led to a significant reduction in oxidative stress, which was evidenced by the data on the stabilization of the ascorbate content and the activity of ascorbate peroxidase. In addition, Thy2 markedly reduced Cd-induced membrane lipid peroxidation and electrolyte leakage in the plants. Thus, the findings demonstrated the ability of the R. leguminosarum strain Thy2, isolated from T. hybridium nodules, to exert a growth-promoting and anti-stress effect on wheat plants. These results suggest that the Thy2 strain may enhance wheat plant growth by mitigating Cd stress, particularly through improving photosynthesis and antioxidant capacity and reducing the severity of oxidative damage. This may provide a basic and biological approach to use the Thy2 strain as a promising, eco-friendly candidate to combat Cd stress in wheat production.

Effects of Pseudomonas sp. OBA 2.4.1 on Growth and Tolerance to Cadmium Stress in Pisum sativum L.

“…The over-accumulation of ROS led to the excessive synthesis of MDA and an increase in the permeability of the membrane structures. An excess of MDA, the end product of lipid peroxidation, and a depletion of GSH, which is a fundamental molecule regulating mitosis [ 33 , 39 ], led to the inhibition of plant growth under stress [ 32 ].…”

“…CAS-blue agar was prepared as described by Schwyn (1986), with some modifications [ 31 , 32 ]. To prepare 100 mL of the medium, 6.5 g of chrome azurol S was dissolved in 5 mL of water and mixed with 1 mL of a solution containing 1 mM FeCl 3 and 10 mM HCl.…”

Symbiosis under Abiotic Stress and Its Challenges

“…Furthermore, heavy metals are important inorganic pollutants in recent years, such as Cu, Ni, Cd, Zn, Cr, and Pb. The studies of symbiosis with these heavy metals are more limited than light metals, mainly focused on Rhizobium and Ensifer species [60][61][62][63][64][65][66][67]. Some studies indicate that the combination of Rhizobium and arbuscular mycorrhizal fungi (AM) induces plant tolerance under As stress [63].…”

“…Some Rhizobium species can nodulate species of Phaseolus, Trifolium, and Vicia under normal conditions but also can improve the seed germination, biomass, and chlorophyll content in these species under Cd-stress, and their response level depend more on the genotype of the plant associated with these rhizobia. For example, the application of R. leguminosarum and Rhizobium larrymoorei helps to decrease the negative effect on other crops, such as wheat [65] and rice [66]. The way these Rhizobium species survive under Cd-stress could be due to the glutathione accumulation, proline metabolic pathways, and its plant interaction could improve because of the accumulation of several compounds such as antioxidants and putrescine protecting the plant cell besides auxins production, N 2 fixation, and others [65,66].…”

“…For example, the application of R. leguminosarum and Rhizobium larrymoorei helps to decrease the negative effect on other crops, such as wheat [65] and rice [66]. The way these Rhizobium species survive under Cd-stress could be due to the glutathione accumulation, proline metabolic pathways, and its plant interaction could improve because of the accumulation of several compounds such as antioxidants and putrescine protecting the plant cell besides auxins production, N 2 fixation, and others [65,66].…”