Saline-alkaline stress affects wheat seedling growth and rhizobacterial community structure

Abstract:

[Background] Plants can mitigate stress by modulating the structure of rhizosphere microbial community, while the changes of wheat growth and rhizobacterial community structure under saline-alkaline stress remain to be clarified. [Objective] To characterize the growth and rhizobacterial community structure of wheat seedlings under saline-alkaline stress. [Methods] Saline-alkaline stress was simulated via the adjustment of the Na⁺ concentration and pH of Hoagland nutrient solution with NaCl and Na₂CO₃, and MiSeq high-throughput sequencing was employed to determine the bacterial community structure. [Results] Compared with no-stress treatment, the saline stress alone decreased the aboveground dry weight, belowground dry weight, functional leaf chlorophyll content, and available nitrogen in rhizosphere soil by 25.0%, 57.1%, 21.2%, and 42.9%, respectively (P<0.05). The increase in pH reduced plant height, root length, biomass, functional leaf chlorophyll content, and the content of main nutrients (available nitrogen, available phosphorus, and organic matter) and the activities of enzymes (alkaline protease, alkaline phosphatase, sucrase, urease, and dehydrogenase) in rhizosphere soil (P<0.05). Three phyla (Proteobacteria,Actinobacteria, and Firmicutes with the relative abundance of 7.1%–71.5%) and five genera (Enterobacter, Methyloversatilis, Azotobacter,Pseudomonas, and Allorhizobium with the relative abundance of 0.5%–5.1%) in the rhizosphere of wheat seedlings were dominant in all the treatments. Saline-alkaline stress had no obvious effect on the alpha diversity indexes, including Shannon index and Chao1, while it significantly affected the beta diversity and changed the community structure. The saline stress alone increased the relative abundance of Flavobacterium, Pseudomonas, Methyloversatilis,Azotobacter, and some unclassified genera by 0.27%–3.12%. The increase in pH increased the relative abundance of Enterobacter, Noviherbaspirillum, and Bacteroidetes. [Conclusion] Saline-alkaline stress significantly inhibited the growth of wheat seedlings and remarkably changed the rhizobacterial community structure. The increased relative abundance of bacterial taxa such as Enterobacter in response to saline-alkaline stress may promote the growth of wheat seedlings and be major microbial sources for improving the crop productivity in saline fields.

Key words:saline-alkaline stress;wheat;rhizobacteria;available nutrients