三七连作土壤细菌、真菌和原生生物群落的差异及驱动因素分析

Variation trends and drivers of bacterial, fungal, and protist communities in the soil with continuous cultivation of Panax notoginseng

摘要:

【背景】 连作障碍是一种存在于农业生产中的常见现象，连作促使植株根际土壤中的养分比例失衡及微生物群落结构失衡，导致植株遭受病虫害等侵袭。【目的】 揭示三七(Panax notoginseng)连作及根腐病发生过程中根际土壤的多元生物群落差异变化规律及驱动因素。【方法】 对不同生长年限的健康与患病三七根际土壤细菌、真菌、原生生物群落差异，以及与土壤因子的相互关系进行研究。【结果】 种植三七土样pH值均小于7.0，土样中重金属镉(Cd)、砷(As)含量超标，镉在3年生样品中表现出显著富集的特征。α多样性结果显示，2年生患病三七显著降低了细菌、真菌群落的多样性，而1年和3年生患病三七显著降低了原生生物群落的多样性。主坐标分析(principal coordinate analysis, PCoA)表明三七连作中细菌、真菌和原生生物群落的β多样性均表现出显著性差异，其中真菌群落在患病前后的差异性最为明显。原生生物群落功能分类分析表明，相对于寄生虫和光养生物，消费者在土壤样本中的类群最多。方差分析表明3年生患病三七土壤样品中消费者的丰度显著降低。真菌病原菌、细菌和原生生物群落的共现网络分析显示，真菌病原菌与原生生物类群间有更多的种间联系，其中占主导的原生生物类群是消费者。相关分析表明速效钾(available potassium, AK)对细菌和真菌的影响最大，镉对细菌、真菌和原生生物群落的影响均大于砷。【结论】 土壤根际多元生物群落差异和土壤理化性质相互作用导致了三七连作根腐病的发生。

Abstract:

[Background] Continuous cropping is a common phenomenon in agricultural production. Continuous cropping causes an imbalance of micronutrients and disturbs the microbial community structure in the rhizosphere soil of plants. Accordingly, plants are susceptible to pests and diseases. [Objective] To expose the variation trends and drivers of distinct biological communities in the rhizosphere soil of Panax notoginseng during continuous cropping and the occurrence of root rot. [Methods] We compared the bacterial, fungal, and protist communities in the rhizosphere soil samples of healthy and diseased P.notoginseng growing for different years and the relationships between soil microbial communities with soil factors. [Results] The soil samples presented pH<7.0, with the content of cadmium (Cd) and arsenic (As) exceeding the standard limits. Cadmium was significantly enriched in the soil samples of 3-year-old P.notoginseng. The results of α-diversity analysis showed that the disease of 2-year-old P.notoginseng significantly reduced the diversity of bacteria and fungi, and the disease of 1- and 3-year-old P.notoginseng significantly reduced the diversity of protist. The principal coordinate analysis showed that the β-diversity of bacterial, fungal, and protist communities in the rhizosphere soil of P.notoginseng exhibited significant differences before and after the infection with root rot, with the fungal community showing the most apparent differences. In the protist community, consumers were richer than parasites and phototrophs in the soil samples. The analysis of variance showed a considerable decrease in the abundance of consumers in the soil samples of diseased 3-year-old P.notoginseng. The co-occurrence network of fungal pathogens with bacteria and protist showed more interspecific associations between fungal pathogens and protist, with consumers being dominant in the protist community. The correlation analysis showed that available potassium had larger effects on bacteria and fungi. Cd, had more significant effects than As on the bacterial, fungal, and protist communities. [Conclusion] The differences in bacterial, fungal, and protist communities in rhizosphere soil and the interactions between microorganisms and physicochemical properties of soil result in the occurrence of root rot in the field with continuous cropping of P.notoginseng.