连作对再植枸杞根际细菌群落多样性和群落结构的影响

Effects of Monocropping on Diversity and Structure of the Bacterial Community in Rhizosphere of Replanted Lycium barbarum L.

受枸杞道地产区土地资源等因素限制,连作障碍已成为影响枸杞产业发展的重要原因之一,导致严重的经济损失。研究连作条件下枸杞农田土壤生态系统微生物群落的演替规律对枸杞产业的可持续发展具有重要的理论意义。以宁夏银川市南梁农场连作多年的枸杞地为研究对象,利用Illumina MiSeq测序技术分析了连作对再植枸杞根际/非根际细菌群落的影响。结果表明,连作地显著抑制再植枸杞苗地径的增加,且其土壤pH较对照样地显著降低(p<0.05)。测序结果证实,与对照样地相比,连作地再植枸杞根际土壤细菌物种数显著降低(p<0.05),细菌群落α多样性下降(p>0.05)。主坐标分析表明,连作和对照样地间枸杞非根际细菌群落结构无明显差异,但连作显著改变再植枸杞根际细菌的群落结构。对细菌群落丰度的统计分析发现,连作地枸杞根际浮霉菌门、非根际假单胞菌门的相对丰度较对照样地显著降低(p<0.05)。此外,冗余分析结果表明:枸杞园土壤pH和有效磷含量是影响枸杞非根际土壤细菌群落结构变化的主要因素,分别解释了41.8%和35.4%的群落结构变化(p<0.05),其他土壤因子无统计学意义,但土壤理化因子对再植枸杞根际细菌群落结构变化的影响均未达显著水平。这些结果证实连作能够显著抑制再植枸杞生长、影响再植枸杞根际细菌群落结构和多样性,干扰枸杞与土壤细菌群落间的互作关系。这些研究结果将为解析枸杞连作障碍机制提供理论基础。

[Objective] Owing to the limitation of soil resources in the traditional wolfberry （Lycium barbarum L. ） production regions, monocropping of the plants has become one of the major factors affecting sustainable development of the industry of wolfberry production and causing serious economic loss every year in Ningxia. It is, therefore, of great theoretic significance to sustainable development of the industry to explore effects of monocropping of the plants on evolution of the soil microbial community in the soil ecosystem. A wolfberry plantation, the Nanliang Farm in Yingchuan of Ningxia was selected as the subject for the study. The Illumina MiSeq sequencing technique was used to analyze the effects. [Method] Soil samples were collected form rhizosphere and bulk soils of the monocropping wolfberry fields and control （ non-monocropping field） for analysis of diversity and structure of the soil microbial communities, and plant samples were, too, for characterization of plant growth. Total genomic DNA was isolated form the rhizosphere and bulk soils using a Power Soil DNA Isolation Kit. Then V4 sections of 16S rDNA were sequenced with the aid of the Illumina MiSeq system and soil microbial communities in the rhizosphere and bulk soils were analyzed for diversity and structure with QIIME. [ Result ] It was found that soil available nitrogen and phosphorus were significantly higher in the monocropping field than in the control, while soil pH and electric conductivity exhibited a reverse trend; that monocropping significantly inhibited growth of the replanted wolfberry. The barcoded pyrosequencing data revealed that in the monocropping field, the number of soil bacterial species in the rhizosphere significantly decreased （p 〈 0.05 ） and the soil bacterial community structure substantially altered as compared with the control＇s However, no much difference in bacterial community diversity and structure was observed in bulk soil between the two fields. Proteobacteria, Actinobacteria, Gemmatimonadetes, Bacteroidetes, Acidobacteria, Cyanobacteria, Firmicutes, Verrucomicrobia, Chloroflexi and Planctomycetes were the most dominant bacterial phyla in all the soil samples, accounting for 93.8% ~ 96.1% of the total taxon tags. Planctomycetes in rhizosphere s abundance in the monocropping field as compared with the control （p 〈 0 gn 05 ificantly decreased in relative level also shows that 40 of the total 579 genera of soil bacteria obviously varied in The analysis at the genera relative abundance between the two treatments （p 〈 0.05 ） . Pearson＇s correlation coefficients analysis also shows that in the bulk soils significantly positive relationships were found between soil pH and Gemmatimonadetes and between nitrate nitrogen content and Proteobacteria, whereas highly negative ones were between Proteobacteria and pH, between Cyanobacteria and total nitrogen content, between Chloroflexi and ammonium nitrogen content, between Actinobacteria and nitrate nitrogen content, between Cyanobacteria and total phosphorus content, and between Firmicutes and available phosphorus content, while in the rhizosphere, positive ones were found between soil pH and Gemmatimonadetes, and between electric conductivity and Planctomycetes, whereas negative ones were between ammonium nitrogen content and Actinobacteria, between available phosphorus content and Gemmatimonadetes, and between available phosphorus content and Planctomycetes. Furthermore, distance based redundancy analysis （ db-RDA ） indicates that soil pH and available phosphorus content were the major factors affecting structure of soil bacterial community in the bulk soil, explained 41.8% and 35.4% of variances （p 〈 0.05 ） , respectively, whereas none of the soil properties was found responsible for the changes in the soil bacterial community structure in the rhizosphere. [Conclusion] All the findings in this experiment demonstrate that monocropping of Lycium barbarum L. has caused serious soil problems, which in turn affect activity and composition of the soil bacterial community in the rhizosphere of the replanted Lycium barbarum L.