盐碱胁迫对小麦幼苗生长和根际细菌群落结构的影响

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

摘要:

【背景】植物可通过改变根际微生物群落结构来减轻胁迫，但盐碱胁迫下小麦生长和根际细菌群落结构变化尚待明晰。【目的】明确盐碱胁迫下小麦幼苗生长及根际细菌群落结构变化。【方法】以添加NaCl和Na₂CO₃调节Hoagland营养液Na⁺浓度和pH来模拟盐碱胁迫，通过MiSeq高通量测序分析细菌群落结构。【结果】与无胁迫对照相比，单纯盐胁迫使小麦幼苗地上和地下部干重、叶绿素和根际土壤速效氮含量分别显著降低了25.0%、57.1%、21.2%和42.9% (P<0.05)；小麦幼苗生长指标和根际土壤速效氮、速效磷、有机质含量及酶活性(除过氧化氢酶)随碱度升高而降低；所有处理的小麦幼苗根际优势菌门(丰度7.1%−71.5%)均为变形菌门(Proteobacteria)、放线菌门(Actinobacteria)和厚壁菌门(Firmicutes)，优势属(丰度0.5%−5.1%)有肠杆菌属(Enterobacter)、嗜多甲基菌属(Methyloversatilis)、固氮菌属(Azotobacter)、假单胞菌属(Pseudomonas)和异根瘤菌属(Allorhizobium)。盐碱胁迫未显著影响根际细菌Shannon指数和Chao1指数，但显著影响群落结构；盐胁迫显著提高了黄杆菌属、假单胞菌属、嗜多甲基菌属、固氮菌属和一些未分类属的丰度，而肠杆菌属和新草螺菌属、拟杆菌门丰度随碱浓度增加而显著提高。【结论】盐碱胁迫显著抑制小麦幼苗生长并改变了根际细菌群落结构，丰度随碱胁迫加重而显著提高的肠杆菌等类群可能是促进盐碱胁迫下小麦生长和提高其盐碱地产能的重要微生物资源。

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.