玉米-大豆轮作模式下根际促生放线菌的筛选及合成菌群的促生效果

Screening of plant growth-promoting Actinomycetes strains and evaluation of plant growth-promoting effect of the synthetic microbial consortium in a maize-soybean rotation system

摘要:

目的 挖掘玉米-大豆轮作模式下玉米根际土壤中的植物根际促生菌(plant growth promoting rhizobacteria, PGPR)资源，明确其在玉米与大豆生长过程中的功能，为农业可持续发展提供微生物层面的理论依据与实践支撑。 方法 采用稀释涂布法，以高氏一号培养基为分离介质，分离玉米根际土壤中的放线菌，并筛选出具备蛋白酶分泌、产铁载体以及固氮能力的促生菌株。运用形态学观察结合16S rRNA基因序列分析技术，对筛选所得菌株进行鉴定。经发酵条件优化和耐胁迫能力测试后，获得复合菌株发酵液合成菌群(synthetic microbial consortium, SMC)。通过促生试验，验证其对玉米和大豆生长的促生作用。 结果 从玉米根际土壤中分离获得105株放线菌，其中5株菌株同时具备产蛋白酶、产铁载体和固氮能力。经鉴定，确定JM-18、JM-21为波卡利水稻节杆菌( Arthrobacter pokkalii)，JM-24为水稻节杆菌( Arthrobacter oryzae)，JM-47为 Arthrobacter ginsengisoli，JM-48为滋养节杆菌( Arthrobacter pascens)。同时发现，这5株菌均具备一定的解无机磷和产NH ₃能力。之后，按1:1的比例将其复配，构成合成菌群SMC。促生试验结果显示，SMC处理对玉米种子发芽和盆栽玉米的生长发育均具有显著促生作用，玉米种子根长和芽长分别增加120.22%、20.94%，盆栽玉米的株高、根长、鲜重、干重均显著提升。此外，SMC对大豆的生长发育同样表现出显著促进效果，可使大豆种子芽长增长42.08%，盆栽大豆的株高、根长、鲜重、干重分别增长39.40%、93.31%、161.14%、163.57%。 结论 本研究筛选出5株兼具产蛋白酶、产铁载体和固氮能力的放线菌，其构建的合成菌群SMC能够显著促进玉米和大豆的生长，为开发高效、环保的微生物肥料提供了极具潜力的优质菌株资源。

Abstract:

Objective To explore plant growth promoting rhizobacteria (PGPR) resources from the rhizosphere soil of maize in a maize-soybean rotation system and elucidate their roles in promoting the growth of maize and soybean, thus providing a theoretical basis and practical support at the microbial level for the sustainable development of agriculture. Methods Actinomycetes strains were isolated from the rhizosphere soil of maize via the dilution plating method with Gauze’s Synthetic Medium No. 1. The strains capable of secreting protease, producing siderophores, and fixing nitrogen were selected out. The isolated strains were identified by means of morphological observation and 16S rRNA gene sequence analysis. After optimization of the fermentation conditions and tests of stress tolerance, a synthetic microbial consortium (SMC) was prepared. Its growth-promoting effects on maize and soybean were evaluated through seed germination tests and pot experiments. Results A total of 105 Actinomycetes strains were isolated, five of which simultaneously exhibited the abilities of siderophore production, protease secretion, and nitrogen fixation. These strains were identified as Arthrobacter pokkalii (JM-18, JM-21), A. oryzae (JM-24), A. ginsengisoli (JM-47), and A. pascens (JM-48). They were mixed in equal proportions to form a SMC. Growth promotion assays showed that the SMC significantly improved maize seed germination and maize plant growth in pots. Specifically, the SMC increased the root length and shoot length in the seed germination assay by 120.22% and 20.94%, respectively, and it also significantly increased the plant height, root length, fresh weight, and dry weight of maize plants in pots. Moreover, the SMC markedly promoted soybean development, increasing soybean shoot length by 42.08% during seed germination. For potted soybean plants, the SMC increased the plant height, root length, fresh weight, and dry weight by 39.40%, 93.31%, 161.14%, and 163.57%, respectively. Conclusion We successfully identified five Actinomycetes strains capable of secreting protease, producing siderophores, and fixing nitrogen. The SMC constructed from these strains significantly enhances the growth of both maize and soybean. This study offers promising microbial resources for the development of efficient and environmentally friendly biofertilizers.