羊草根际耐盐促生菌的筛选鉴定及促生效果

Screening, identification, and growth-promoting effect evaluation of salt-tolerant rhizosphere bacteria of Leymus chinensis

摘要:

【背景】 发掘根际耐盐微生物对于盐碱地改良利用和缓解植物盐胁迫具有重要意义。【目的】 筛选种植在盐碱地的羊草(Leymus chinensis)根际促生菌，分析其生长特性及促生效果，并探究其对羊草种子萌发的影响，为根际促生菌的开发应用提供科学依据。【方法】 从羊草根际土壤中分离出菌株，用不同盐浓度和不同pH值的LB培养基测定菌株耐盐能力及pH适应性，用Salkowski比色法测定其产吲哚乙酸(indole-3-acetic acid, IAA)能力，用钼锑抗比色法和CAS培养基测定菌株的解磷和产铁载体能力。结合形态、生理生化及16S rRNA基因测序，筛选出优势促生菌株。通过种子萌发试验来验证其促生效果，开展菌株与羊草幼苗互作的盐胁迫盆栽试验，测定不同处理下羊草幼苗的生长及生理指标。【结果】 筛选得到3株高效多功能促生菌株：盐角木罗塞略莫拉氏菌(Rossellomorea arthrocnemi) Z7、海水罗塞略莫拉氏菌(Rossellomorea aquimaris) Z25、大洋沉积物泡状芽孢杆菌(Cytobacillus oceanisediminis) Z49；3株菌均可在盐浓度为0%-9%、pH值在8.85-10.00的LB培养基上存活，其产IAA能力分别为10.10、7.74、17.44 mg/L，解无机磷能力分别为107.80、128.52、95.95 mg/L，其中菌株Z25还具有产铁载体能力。羊草种子萌发试验可知，相较于对照组，3株菌使种子发芽率分别提高5.45%、16.36%、13.64%。对根长的提升率分别为17.86%、31.79%、27.14%。盆栽试验表明接菌可降低羊草幼苗丙二醛(malondialdehyde, MDA)含量，提高抗氧化酶含量。【结论】 菌株Z7、Z25、Z49是兼具产IAA、溶磷、耐盐碱的多功能促生菌，可为开发生物制剂提供优良菌株资源，提高盐碱地的利用率。

Abstract:

[Background] Exploring salt-tolerant rhizosphere microorganisms is of great significance for improving and utilizing saline-alkali land and for alleviating plant salt stress. [Objective] To screen plant growth-promoting rhizobacteria (PGPR) of Leymus chinensis planted in saline-alkali soils, analyze their growth characteristics and plant growth-promoting effects, and explore their effects on seed germination of L. chinensis, thus providing a scientific basis for the development and application of PGPR. [Methods] The strains were isolated from the rhizosphere soil of L. chinensis. The salt tolerance and pH adaptability of the strains were tested in LB media with different salt concentrations and pH values. The ability to produce indole-3-acetic acid (IAA) was determined by the Salkowski colorimetric method. The molybdenum-antimony colorimetric method and CAS medium were used to assess the abilities of the strains to solubilize phosphorus and produce siderophores, respectively. The strains were identified based on morphological, physiological, biochemical, and 16S rRNA gene sequencing, and the dominant strains with plant growth-promoting effects were screened. Seed germination tests were conducted to verify the plant growth-promoting effects of the strains. Pot experiments on the interactions between strains and L. chinensis seedlings under salt stress were carried out to determine growth and physiological indicators of the seedlings under different treatments. [Results] Three efficient multifunctional strains with plant growth-promoting effects were screened out: Rossellomorea arthrocnemi Z7, Rossellomorea aquimaris Z25, and Cytobacillus oceanisediminis Z49. They could survive in LB media with salt concentrations of 0%–9% and pH 8.85–10. Z7, Z25, and Z49 showed the IAA production capacity of 10.10, 7.74, and 17.44 mg/L and the inorganic phosphorus-solubilizing capacity of 107.80, 128.52, and 95.95 mg/L, respectively. Among them, strain Z25 produced siderophores. Compared with the control group, Z7, Z25, and Z49 increased the seed germination rate by 5.45%, 16.36%, and 13.64% and the root length by 17.86%, 31.79%, and 27.14% respectively. Inoculation of the three strains reduced the MDA content and increased the content of antioxidant enzymes of L. chinensis seedlings in Pot experiments. [Conclusion] Strains Z7, Z25, and Z49 are multifunctional bacteria that produce IAA, solubilize phosphorus, and tolerate saline-alkali. They can serve as excellent strain resources for the development of bioinoculants and improve the utilization rate of saline-alkali soil.