Pseudarthrobacter sp. from Hordeum marinum enhances wheat salt tolerance by modulating antioxidant enzymatic activity and reducing oxidative damage.

Abstract

Background: Wheat (Triticum aestivum L.) is a globally important crop, but its production is limited by soil salinity, which accounts for up to 15 million metric tons of yield loss annually. The use of salt tolerant rhizobacteria from halophytic plants offers a promising strategy for improving crop resilience to salinity. This study is the first to investigate the potential of rhizobacteria from sea barley (Hordeum marinum), which thrives in saline environments, to enhance salt stress tolerance in wheat.

Results: A total of 13 rhizospheric bacterial isolates were recovered from H. marinum, and five isolates, namely Bacillus sp., Microbacterium sp., Paenarthrobacter sp., Arthrobacter sp., and Pseudarthrobacter sp., were selected based on their salt (NaCl) tolerance using 300 mM, 600 mM, and 900 mM NaCl. The selected isolates were applied to wheat plants grown in trays under controlled greenhouse conditions, individually and as a consortium, under 100 mM NaCl treatment. Shoot fresh weight, shoot length, and water status were measured to evaluate physiological responses at the time of harvesting, when visible salt stress symptoms such as leaf rolling and browning were observed. Reactive oxygen species (H₂O₂ and OH⁻), malondialdehyde (MDA) levels, proline content, and antioxidant enzymatic activities (superoxide dismutase, catalase, ascorbate peroxidase) were also determined to assess the effect of the most growth promoting bacteria on these selected biochemical components. Inoculation with Paenarthrobacter sp., Arthrobacter sp. and Pseudarthrobacter. sp. enhanced shoot fresh weight under salt treatment by 11%, 13% and 16%, respectively, and increased shoot length by 7%, 5% and 11%, respectively. Under salt stress, plants inoculated with Pseudarthrobacter sp. showed lower MDA levels in both leaves and roots, along with significantly higher catalase activity in leaves and increased superoxide activity in the roots compared to uninoculated plants.

Conclusions: These findings demonstrate that the halotolerant isolate S9 (Pseudarthrobacter sp.) enhances wheat tolerance to salinity by improving plant growth, maintaining plant water status, reducing oxidative damage, and modulating antioxidant enzyme activities. These results highlight the potential of halotolerant rhizobacteria from H. marinum as sustainable bioinoculants for improving wheat production in salt-affected soils.