德庆贡柑根围土壤及叶际细菌的分离与植物促生功能

Isolation and plant growth-promoting function evaluation of bacteria from rhizosphere soil and phyllosphere of Citrus reticulata cv. Gonggan in Deqing

摘要:

德庆贡柑(Citrus reticulata cv. Gonggan in Deqing)作为中国国家地理标志产品，其品质形成与微生物生态密切相关。深入探究贡柑相关微生物资源对提升贡柑品质和产量意义重大。目的 分离培养德庆贡柑根围土壤及叶际表面的细菌，系统评价其促植物生长功能，为德庆贡柑的绿色栽培提供可用的促生菌资源。方法 分别采集德庆贡柑根围土壤及叶片样本，采用稀释涂布法分离样本中的细菌，根据16S rRNA基因序列同源性鉴定菌株。利用溶磷、解钾、固氮和产铁载体的功能培养基评价菌株的促生能力，筛选高活性菌株。通过盆栽试验验证筛选出的菌株的促生功能。结果 本研究共分离得到240株细菌，其中从贡柑根围土壤分离出96株，从叶际分离出144株。这些菌株隶属于4门29科51属，其中假单胞菌门(Pseudomonadota)为优势门，芽孢杆菌科(Bacillaceae)为优势菌科。240株细菌中，230株菌具有溶磷、解钾、固氮、产铁载体和产吲哚-3-乙酸(indole-3-acetic acid, IAA)中的一种能力，占比达95.83%；123株菌具有3种以上促生能力，占比为51.25%。鉴于德庆贡柑的生长周期较长，本研究以番茄作为模式植物，通过盆栽试验评价8株具有2种及以上功能的菌株的促生功能。供试菌株显著增加了番茄的株高和鲜重。结论 德庆贡柑根围土壤和叶际蕴含着丰富的功能微生物资源。本研究成功筛选出多株促生细菌菌株，盆栽试验证明它们能显著促进番茄生长。研究结果为德庆贡柑微生物资源的开发利用以及绿色栽培技术的发展提供了坚实的理论依据。

Abstract:

Citrus reticulata cv. Gonggan in Deqing is a national geographical indication product of China, and its quality formation is intricately linked to microbial ecology. In-depth exploration of the microbial resources associated with Gonggan is of great significance for enhancing the quality and increasing the yield of this fruit.Objective To isolate and culture bacteria from the rhizosphere soil and phyllosphere surface of Gonggan in Deqing and systematically evaluate their plant growth-promoting functions, thus providing applicable bacterial resources for the eco-friendly cultivation of Gonggan in Deqing.Methods Samples of rhizosphere soil and leaves of Gonggan in Deqing were collected. Bacteria within the samples were isolated via the dilution plating method. Bacterial strains were identified based on the homology of their 16S rRNA gene sequences. The functional media for phosphate solubilization, potassium release, nitrogen fixation, and siderophore production were used to evaluate the plant growth-promoting ability of bacterial strains, and the strains with strong plant growth-promoting functions were screened out. Ultimately, pot experiments were conducted to validate the plant growth-promoting functions of the selected strains.Results A total of 240 bacterial isolates were obtained, including 96 strains from the rhizosphere soil and 144 strains from the phyllosphere. These strains belonged to 51 genera, 29 families of 4 phyla, where Pseudomonadota was the dominant phylum and Bacillaceae was the dominant family. Functional characterization revealed that 230 (95.83%) strains exhibited at least one plant growth-promoting function, while 123 strains (51.25%) possessed three or more such functions. Given the extended growth cycle of Gonggan in Deqing, we utilized tomato as a model plant to evaluate the plant growth-promoting functions of eight bacterial strains possessing at least two functions through pot experiments. The results demonstrated that the tested strains significantly increased both plant height and fresh weight of tomato plants.Conclusion The rhizosphere soil and phyllosphere of Gonggan in Deqing harbor abundant functional microbial resources. This study successfully screened multiple strains of plant growth-promoting bacteria, and pot experiments demonstrated their significant ability to promote tomato growth. These findings provide a solid theoretical foundation for exploiting microbial resources of Gonggan in Deqing and advancing eco-friendly cultivation practices.