一株高产吲哚乙酸促生菌的筛选鉴定、条件优化、应用效果及其代谢途径

A high indole-3-acetic acid-producing bacterial strain with plant growth-promoting effect: screening, identification, culture condition optimization, application, and genome-wide analysis

摘要:

【背景】华北平原潮土和砂姜黑土对国家粮食安全至关重要，但由于土壤结构障碍和长期不合理利用，影响冬小麦的萌发和生长。【目的】筛选出具有高产吲哚乙酸(indole-3-acetic acid, IAA)能力的菌株，并优化其培养条件，开展室内和田间试验，结合基因组测序分析IAA代谢途径。【方法】采集华北平原潮土和砂姜黑土的小麦根际土壤，通过稀释涂布平板法筛选菌株，并进行IAA定性和定量分析；探讨不同pH和NaCl浓度下的最适生长条件；结合形态学、生理生化及16S rRNA基因序列分析对其种属进行鉴定；通过小麦种子发芽试验及盆栽试验验证其促生效果，并制备菌剂应用于大田试验，评估增产效果；基于全基因组测序分析其IAA合成代谢通路。【结果】筛选出一株IAA产量达到58.9 mg/L的栗褐芽孢杆菌(Bacillus badius) 363，其最适生长条件为pH 6.0、NaCl浓度为1%；种子萌发和盆栽试验表明，菌株363能促进小麦种子的发芽和根系生长，芽长和根长分别提高72.9%和161.8%，并且显著促进了小麦植株的生长，株高、地上生物量和根系干重在潮土和砂姜黑土上分别提高35.7%和22.6%、17.4%和33.3%、33.3%和36.4%。田间试验中，菌株363在潮土和砂姜黑土上使小麦产量分别提高10.8%和8.25%。全基因组分析表明菌株363有2条产IAA代谢通路。【结论】栗褐芽孢杆菌363在冬小麦促生方面具有很好的潜力，未来在高效根际促生菌剂、生物肥料的开发中具有广泛的应用前景。

Abstract:

[Background] The fluvo-aquic soil and Shajiang black soil in the north China Plain are critical to national food security. However, structural barriers in the soil and long-term improper utilization have negatively impacted the germination and growth of winter wheat. [Objective] To screen out the bacterial strains with high indole-3-acetic acid (IAA) production, optimize their growth conditions, examine their application performance by laboratory and field experiments, and analyze the IAA biosynthetic pathways by genome-wide analysis. [Methods] fluvo-aquic and Shajiang black soil samples were collected from wheat rhizosphere. The strains were screened by the dilution plate method, and their IAA production was analyzed qualitatively and quantitatively. The optimal growth conditions were determined under varying pH and NaCl concentrations. The strain was identified based on morphological, physiological, and biochemical characteristics and 16S rRNA gene sequencing results. Seed germination and pot experiments were conducted to assess the growth-promoting effects of the strain screened out on the plants. A bacterial inoculant was prepared and applied in field trials to evaluate its effect on wheat yield. Genome-wide analysis was performed to analyze the IAA biosynthetic pathways. [Results] A strain 363 which produced IAA at a concentration of 58.9 mg/L was identified as Bacillus badius. The optimal growth conditions were pH 6.0 and 1% NaCl. Seed germination and pot experiments showed that strain 363 significantly promoted wheat seed germination and increased the bud length and root length by 72.9% and 161.8%, respectively. Moreover, strain 363 promoted wheat plant growth, increasing the plant height, shoot biomass, and root dry weight by 35.7% and 22.6%, 17.4% and 33.3%, and 33.3% and 36.4% in fluvo-aquic soil and Shajiang black soil, respectively. In field trials, strain 363 increased wheat yields by 10.8% and 8.25% in fluvo-aquic soil and Shajiang black soil, respectively. Genome-wide analysis revealed that strain 363 had two IAA biosynthetic pathways. [Conclusion] B. badius 363 has great potential to promote the growth of winter wheat and demonstrates broad application prospects in the development of efficient plant growth-promoting rhizobacterial inoculants and biofertilizers.