不同种植模式下丹参根际土壤微生物群落结构变化

采用MiSeq高通量测序技术对连作、轮作、套作3种种植模式下丹参根际土壤中细菌的16S rDNA基因V3—V4区片段和真菌18S rDNA基因V4区片段进行了测序,研究了细菌和真菌群落结构的变化,并分析了其与土壤因子的关系,从根际微生态系统的变化阐释了丹参连作障碍的发生机理。总体上,细菌和真菌群落的大部分Alpha多样性指数在3种种植模式之间没有显著差异,但呈现轮作套作连作的趋势。与连作相比,轮作显著提高了细菌群落的香农-威纳指数和丛枝菌根真菌的侵染率。从细菌群落的组成上看,轮作模式下芽单胞菌门的相对丰度显著低于连作和套作。相反,轮作和套作时浮霉菌门和拟杆菌门的相对丰度则高于连作。轮作和套作模式下,真菌群落中的接合菌门、壶菌门和子囊菌门的相对丰度显著高于连作。另外,不同种植模式下微生物之间的相互作用关系也有明显差异,轮作甚至会造成真菌之间的相互关系发生逆转。连作模式下检出了丹参枯萎病的病原菌镰刀菌,而有益菌枯草杆菌属的数量却呈下降趋势,这可能是引起丹参病害加剧的原因之一。主坐标成分分析表明,微生物群落在3种种植模式之间没有发生显著的分化,前两个主坐标成分的总解释能力均小于30%,表明没有显著的主导因子。轮作和套作可以提高土壤pH和部分矿质营养,降低ORP。但是,土壤性质的变化仅影响细菌群落,对真菌群落的影响不明显。套作模式下,总钾和有效钾会提高细菌和真菌群落的多样性;轮作和连作模式下的真菌群落则刚好相反,它们更适应低钾和高ORP的环境。研究结果表明,轮作和套作可以在一定程度上改善土壤质量,提高根际细菌群落多样性,改变微生物群落组成,以及微生物-微生物、微生物-丹参之间的相互关系,这些可能是缓解丹参连作障碍的重要原因。

Variation in microbial community structure in the rhizosphere soil of Salvia miltiorrhiza Bunge under three cropping modes

Salvia miltiorrhiza Bunge, a staple in Chinese herbal medicine, is widely used for the treatment of cardiovascular diseases. However, the yield and quality of S. miltiorrhiza have decreased dramatically because of severe continuous cropping obstacles stemming from inadequate wild resources and limited genuine production areas. The rhizosphere soil samples of S. miltiorrhiza under three cropping modes-rotation cropping monoculture (RCMO), continuous cropping monoculture (CCMO), and intercropping mix-culture (ICMI)-were collected from the city of Bozhou in the Anhui province. The MiSeq high-throughput sequencing technique, targeting the V3-V4 region of the bacterial 16S rDNA gene and the V4 region of the fungi 18S rDNA gene, was used to investigate the bacterial and fungi community structure and analyze the links between the microbial community structure and soil environmental parameters. The goal of this study was to illuminate the mechanism of continuous cropping obstacles that occur in S. miltiorrhiza from the perspective of a rhizospheric micro-ecological environment. Overall, most Alpha diversity indexes of microbial communities followed the order of RCMO > ICMI > CCMO, but significant differences were not observed between the three cropping modes. The Shannon-Wiener index of bacterial community and the mycorrhizal colonization of S. miltiorrhiza under RCMO were higher than those under CCMO. The relative abundance of the top 10 dominant bacterial phyla accounted for 94%, and all of the 10 dominant phyla were the same across all cropping modes; these were Proteobacteria, Acidobacteria, Gemmatimonadetes, Planctomycetes, Actinobacteria, Bacteroidetes, Verrucomicrobia, Unclassified, Firmicutes, and Chloroflexi phyla. In terms of bacterial community composition, the relative abundance of Gemmatimonadetes phylum under RCMO was lower than that under CCMO and ICMI. In contrast, the dominance of Planctomycetes and Bacteroidetes phyla under RCMO and ICMI were higher than that under CCMO. In total, only nine fungi phyla were found in this study, most of them unclassified fungi. The relative abundance of Zygomycota, Chytridiomycota, and Ascomycota phyla under RCMO and ICMI increased compared to CCMO. Furthermore, the relationship between the microbes differed significantly across the three cropping modes. The rotation of S. miltiorrhiza even reversed the relationship between fungi, from negative undehttp://toutiao.7junshi.com/?qid=minitopr CCMO to positive. The ratio of beneficial Bacillus genus decreased but pathogenic Fusarium genus increased under CCMO, which might change the relationship between the microbial community and dramatically exacerbate the diseases of S. miltiorrhiza. Differentiations between the microbial communities were not evident between the three cropping modes according to principal coordinates analysis (PCoA). The variation in microbial communities was controlled by eight principal coordinates, among which the first two principal coordinates explained less than 30% of the total variance. This indicates that there was no dominant factor that shaped the microbial community. The results showed that soil pH, ORP, and partial mineral nutrients were improved under RCMO and ICMI modes compared to CCMO. A Monte Carlo permutation test revealed that soil environmental parameters were closely related to the differences in the bacterial community but not the fungi community. Total and available K were positively correlated to bacterial and fungi communities under ICMI, respectively. In contrast, fungi communities under RCMO and CCMO were better adapted to low available K and high ORP in soil environments. Our study indicated that RCMO and ICMI can, to some extent, improve the physicochemical properties of soil, increase the diversity of microbial community in the rhizosphere soil of S. miltiorrhiza, and change the microbe-microbe and microbe-plant relationships in comparison with CCMO, thus alleviating the continuous cropping obstacles.