种植年限对健康三七根际土壤微生物活性和功能的影响

为研究种植年限对健康三七根际土壤微生物活性和功能的影响，以种植一年和二年的健康三七根际土为研究对象，采用荧光素二乙酸酯水解法、实时荧光定量PCR及Biolog微平板法等技术手段分析土壤微生物活性、氮素循环功能基因丰度、碳源代谢活性及其功能多样性。结果表明，与未种植过三七的土壤相比，三七种植能够显著提高土壤微生物的活性、氮素循环功能基因丰度(nifH和细菌amoA)、碳源代谢活性及其功能多样性，且随着种植年限的增加，健康三七根际微生物活性及其功能逐渐增强。同时，种植年限能够改变健康三七根际微生物的碳源利用特征；但是，根际微生物对酚酸类物质的代谢能力并未随三七种植年限的增加而增加。这也从侧面说明，根际酚酸物质降解能力的不足可能是导致其积累并驱动根际微生态失衡和形成连作障碍的重要原因。这些研究结果不仅为深入了解健康三七根际微生物活性及其代谢功能特征提供了数据支撑，也为解析三七连作障碍的形成机理提供了一定的理论依据。

Effect of Planting Years on Rhizosphere Soil Microbial Activity and Function of Healthy Sanqi Ginseng

Sanqi ginseng (Panax notoginseng (Burk.) F. H. Chen) is a highly valuable medicinal herb that could be geo-authentically produced in a restricted area of southwest China. Continuous cropping obstacles has seriously threatened the sustainable production of Sanqi ginseng and causes great economic losses annually. Increasing evidences documented that the loss of specific degradation function of rhizosphere microbes may be the chief culprit in causing continuous cropping obstacles. In order to study the effect of planting years on the rhizosphere soil microbial activity and function of healthy Sanqi ginseng, rhizosphere soils of 1- and 2-year-old healthy Sanqi ginseng were collected and fluorescein diacetate hydrolysis method, real-time quantitative PCR and Biolog assay were employed to analyze the soil microbial activity, nitrogen functional gene abundances, metabolic activity and functional diversity. Results showed that the Sanqi ginseng planting significantly enhanced the soil microbial activity as compared to the uncultivated soil, and the soil microbial activity continuously increased with the growth of Sanqi ginseng. Similarly, the abundances of nitrogen-related functional genes (nifH and bacteria amoA) also increased in response to the Sanqi ginseng cultivation and planting years, indicating that the nitrogen availability might be enhanced by the rhizosphere microbes and is for the nutrient requirements of Sanqi ginseng. Moreover, rhizosphere soil metabolic activity and functional diversity indices were also improved by Sanqi ginseng planting, and they were increased along with the Sanqi ginseng growth. In addition, Sanqi ginseng planting years could alter the carbon source utilization pattern of rhizosphere microbes. Interestingly, the utilization efficiencies of carbohydrates, carboxylic acids, amino acids, amines, and polymers by rhizosphere microbes were increased with Sanqi ginseng planting years, whereas the utilization efficiency of phenolic acids not differed significantly with the growth of Sanqi ginseng. Therefore, the lack of degradation activity of rhizosphere phenolic acids is an important reason for its accumulation and thereby drives the imbalance of rhizosphere microbiomes as well as the formation of continuous cropping obstacles. These results cannot only provide data support for understanding the rhizosphere microbial activity and metabolic function of healthy Sanqi ginseng, but also provide theoretical basis for the interpretation of formation mechanism of continuous cropping obstacles of Sanqi ginseng.