干旱胁迫对红豆草幼苗生长及根际土壤细菌群落的影响

Influence of simulated drought stress on seedling growth and bacterial communies in the rhizosphere of sainfoin

摘要:

【目的】为旱地红豆草丰产、高效、优质栽培提供理论依据和技术指导。【方法】以红豆草 （Onobrychis viciaefolia）新品系 P1、P2、P3 和甘肃红豆草（O. viciaefolia cv. Gansu）、蒙农红豆草（O. vi- ciaefolia cv. Mengnong）为试验材料，采用营养液沙培法，以-0. 8 MPa PEG-6000 模拟干旱胁迫，研究不同干旱胁迫时间（0、3、6、9 d）对红豆草幼苗生长及根际土壤细菌群落结构的影响。【结果】随干旱胁迫时间延长，红豆草株高和根平均直径呈增大趋势；叶面积显著减小（P＜0. 05）；地上干重、根尖数、根长、根表面积、根体积均显著增加（P＜0. 05）；地下干重、根冠比、根系活力先增大后减小（P＜0. 05），并在胁迫 3 d 时达到最大。在整个胁迫期间，新品系 P1 的根尖数、根直径、地上干重、地下干重均值高于其他材料。Chao1、ACE、Simpson 和 Shannon-wiener 指数先降低后增加（P＜0. 05），在 0 d 时最大，前二者在 6 d 时最小，而后二者在 3 d 时最小。根际土壤细菌群落以变形菌门、厚壁菌门、疣微菌门、拟杆菌门和放线菌门为主，干旱胁迫时间显著增加了变形菌门的相对丰度（P＜0. 05），显著降低了厚壁菌门、 放线菌门和疣微菌门的相对丰度（P＜0. 05），但蓝藻菌门和拟杆菌门的相对丰度先降低后增加（P＜ 0. 05）。【结论】干旱胁迫对红豆草幼苗生长及根际土壤细菌群落组成有显著影响。

Abstract:

【Objective】 To study the effects of drought stress on seedling growth and bacterial communities in the rhizosphere of sainfoin.【Method】 Three new sainfoin lines of P1，P2，P3，Onobrychis viciaefolia‘Gansu’ and O. vi- ciaefolia‘Mengnong’ were selected for simulated drought stress experiments. The microcosm experiment was con- ducted under four drought stress treatments by PEG-6000 with a water potential of -0. 8 MPa. Samples of each ma- terial were collected every 3 days. The total DNA of the seedling rhizosphere soil was extracted and deep sequencing of V4 region of 16S rRNA gene was performed to characterize the bacterial community structure of drought-treated sainfoin.【Result】 Results showed that plant height and average root diameter increased，while leaf area decreased sig- nificantly with the extension of stress time. The aboveground biomass，root tip number，total root length，total root surface area，and root volume were significantly increased with increasing drought stress time，whereas underground biomass，root shoot ratio，and root activity significantly increased first and then decreased and reached the most under drought stress of 3 days. The root tip number，average root diameter，aboveground and underground biomass of new sainfoin line of P1 were significantly higher than those of other lines during the whole period of stress. The richness in- dex of Chao1，Ace，Simpson，and Shannon-wiener decreased first and then increased dramatically. Furthermore， Chao1 and ACE indexes were the lowest under drought stress of 6 days，whereas the diversity index of Simpson and Shannon Wiener were the lowest under drought stress of 3 days. Proteobacteria，Firmicutes，Verrucomicrobia，Bacte- roidetes，and Actinobacteria were dominant bacterial phyla. The relative abundance of Proteobacteria dramatically in- creased，while those of Firmicutes，Actinobacteria，and Verrucomicrobia evidently decreased along the stress time， whereas those of Cyanobacteria and Bacteroidetes significantly firstly decreased then increased.【Conclusion】 The re- sults provide reference for sainfoin to resist drought stress and improve water use under drought stress.