模拟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 Community in the Rhizosphere of Sainfoin

【目的】探明干旱胁迫对红豆草(Onobrychis viciaefolia)根系生长及根际土壤细菌群落的影响,为提高红豆草耐旱性和水分利用效率提供理论依据。【方法】采用营养液沙培法,以红豆草新品系P1、P2、P3和甘肃红豆草(O.viciaefolia‘Gansu’)、蒙农红豆草(O.viciaefolia‘Mengnong’)为试验材料,以-0.8 MPa PEG-6000模拟干旱胁迫,比较不同胁迫时间(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】随胁迫时间延长,红豆草株高和根系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指数先降低后增加(P<0.05),在0 d时最大,Chao1、ACE在6 d时最小,而Simpson和Shannon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】新品系P1具有较好的抗旱性;调节微生物群落结构和改善土壤微域环境能提高植物干旱胁迫耐受性。

【Objective】The effects of drought stress on root growth and rhizosphere soil bacterial community of Onobrychis viciaefolia were investigated to provide a theoretical basis for improving drought tolerance and water use efficiency in sainfoin.【Method】The nutrient solution sand culture method was adopted,different sainfoin lines including three new lines of P1,P2,P3,Onobrychis viciaefolia′Gansu′and O.viciaefolia′Mengnong′were used.Drought stress was simulated with PEG-6000 with a water potential of-0.8 MPa of different stress time(0,3,6,and 9 days).The total DNA of the seedling rhizosphere soil was extracted and amplicon sequencing of V4 region of 16S rRNA gene was performed to characterize the bacterial community structure of drought-treated sainfoin.【Result】With the prolonging of stress,the plant height and average root diameter of Onobrychis viciaefolia were increased,while the leaf area was decreased significantly(P<0.05).Aboveground dry weight,root tip number,total root length,total root surface area,and root volume were significantly increased(P<0.05),whereas underground dry weight,root shoot ratio,and root activity firstly increased and then decreased significantly(P<0.05),and reached the maximum at 3 days of drought stress.The mean values of root tip number,root diameter,aboveground and underground dry weights of new sainfoin line of P1 were significantly higher than those of other lines(P<0.05)during the whole period of stress.The indices of Chao1,ACE,Simpson,and Shannon were first decreased and then increased(P<0.05),and reached the maximum at 0 d.Chao1 and ACE indices were the lowest under drought stress of 6 days,whereas the diversity indices of Simpson and Shannon were the lowest under drought stress of 3 days.Proteobacteria,Firmicutes,Verrucomicrobia,Bacteroidetes,and Actinobacteria were dominant bacterial phyla.The drought stress time significantly increased the relative abundance of Proteobacteria,decreased the relative abundance of Firmicutes,Actinobacteria,and Verrucomicrobia,and firstly decreased and then increased the relative abundance of Cyanobacteria and Bacteroidetes significantly(P<0.05).【Conclusion】The new sainfoin line of P1 has better drought resistance.Modifying the microbial community structure and improving the soil microdomain environment can improve the drought stress tolerance of plants.