柠条根际促生芽孢杆菌的分离、鉴定及功能 分析

Isolation, Identification, and Functional Analysis of Plant Growth-Promoting Bacillus Strains Associated with the Rhizosphere of Caragana korshinskii Kom.

摘要: 内蒙古自治区作为我国北方的重要生态屏障，承担着我国23%的防沙重任。柠条(Caragana korshinskii Kom.)作为耐旱植物，在防风固沙和水土保持中发挥重要作用。为保证人工栽培柠条的发芽和幼苗生长，本研究分离筛选柠条根际促生菌、评价其促生性能，构建复合菌剂并通过盆栽实验研究最佳菌种组合，分析菌剂对柠条理化指标、土壤指标和根际微生物的影响。结果表明，从柠条根际土壤和平茬废弃物中分离得到84株芽孢杆菌(Bacillus)，筛选出产吲哚乙酸、解磷、解钾和拮抗功能的菌株11株，其中SGA510、SC21和B180可显著促进柠条种子萌发和幼苗生长(p < 0.05)，萌发率分别提高4%、5%和9.33%，株高分别增长14.23%、10.01%和12.12%，经鉴定，SGA510为植物内芽孢杆菌(B. endophyticus)，SC21和B180为枯草芽孢杆菌(B. subtilis)。构建的SGB (SGA510 + SC21)和SCB (SC21 + B180)复合菌剂能够分别显著提升柠条株高25.3%和27.3%、叶片数30.3%和20.6% (p < 0.05)。此外，两种复合菌剂还能显著提高柠条叶绿素含量和超氧化物歧化酶活力，降低丙二醛含量，提升土壤蔗糖酶活性，且SGB还能显著提高土壤速效磷含量(p < 0.05)。根际微生物分析结果显示，SGA510、SGB和SCB可显著降低根际微生物丰富度(p < 0.05)，但不改变土壤本身菌群结构(p > 0.05)。其中，SC21、SGB和SCB可提高变形菌门(Proteobacteria)丰度(分别为8.2%、7.1%和17.2%)，降低纤维弧菌属(Cellvibrio)丰度，SGA510、SC21、SGB和SCB可提高马赛菌属(Massilia)丰度。综上，本研究筛选出高效促生菌株并构建复合菌剂，改善了柠条根际微环境、提高了柠条生物量，为内蒙古荒漠化地区治理和可持续发展提供了一种微生物解决思路。

Abstract: As an important ecological barrier in northern China, the Inner Mongolia Autonomous Region bears 23% of the nation’s major sand control responsibility. Caragana korshinskii Kom., a drought-tolerant plant, plays a key role in windbreak and sand fixation as well as soil and water conservation. To ensure the germination and seedling growth of cultivated C. korshinskii, this study isolated and screened plant growth-promoting rhizobacteria (PGPR) from the rhizosphere of C. korshinskii, evaluated their growth-promoting traits, constructed composite microbial inoculants, and investigated the optimal bacterial combinations through pot experiments. The effects of the inoculants on the physicochemical indices of C. korshinskii, soil properties, and rhizosphere microbial community were analyzed. Results showed that 84 Bacillus strains were isolated from rhizosphere soil and pruning residues of C. korshinskii. Among them, 11 strains exhibited capabilities such as IAA production, phosphate solubilization, potassium solubilization, and antagonistic activity. Three strains, SGA510, SC21, and B180, significantly promoted seed germination and seedling growth of C. korshinskii (p < 0.05), increasing germination rates by 4%, 5%, and 9.33%, respectively, and plant heights by 14.23%, 10.01%, and 12.12%, respectively. SGA510 was identified as B. endophyticus, while SC21 and B180 were identified as B. subtilis. The composite inoculants SGB (SGA510 + SC21) and SCB (SC21 + B180) significantly increased plant height by 25.3% and 27.3%, and leaf number by 30.3% and 20.6%, respectively (p < 0.05). Moreover, both composite inoculants significantly increased chlorophyll content and superoxide dismutase (SOD) activity, reduced malondialdehyde (MDA) content, and enhanced soil sucrase activity. Additionally, SGB significantly increased soil available phosphorus content (p < 0.05). Rhizosphere microbial analysis revealed that SGA510, SGB, and SCB significantly reduced rhizosphere microbial richness (p < 0.05) but did not alter the overall soil microbial community structure (p > 0.05). Specifically, SC21, SGB, and SCB increased the abundance of Proteobacteria (by 8.2%, 7.1%, and 17.2%, respectively) and reduced the abundance of Cellvibrio; SGA510, SC21, SGB, and SCB increased the abundance of Massilia. In conclusion, this study screened highly efficient growth-promoting bacterial strains and constructed composite inoculants, which improved the rhizosphere microenvironment and increased the biomass of C. korshinskii, providing a microbial approach for desertification control and sustainable development in Inner Mongolia.