茴香轮作调控土壤细菌群落缓解三七连作障碍的效应及机制

三七是我国特有的中药材，但连作障碍严重制约了其产业发展，轮作是生产上最常用且有效的缓解措施。本研究在三七收获后的土壤上轮作茴香，通过测定轮作土壤水浸液对三七存苗的影响来评价轮作对三七连作障碍的缓解效果，并从轮作对土壤细菌群落的影响方面深入阐释轮作缓解连作障碍的机制。结果表明，茴香轮作后的土壤水浸液可以显著提高三七的存苗率。土壤细菌分析表明，茴香轮作后土壤细菌群落发生了明显改变。细菌的丰富度增加，相对丰度>1%的优势菌门变形菌门Proteobacteria和放线菌门Actinobacteria的相对丰度呈增加趋势。属水平上，轮作茴香使66个属的相对丰度显著增加，其中相对丰度>0.2%的优势菌属有14个；30个属的相对丰度显著降低，其中优势菌属有8个，总体上看相对丰度显著增加的属多于显著降低的属。在相对丰度显著增加的优势菌属中包含常见的拮抗菌属假单胞菌属Pseudomonas和芽孢杆菌属Bacillus细菌。本研究也分离到2株假单胞菌和1株芽孢杆菌对三七根腐病菌腐皮镰刀菌Fusarium solani和Monographella cucumerina具有明显的拮抗活性。因此，轮作茴香可以改善三七连作土壤细菌群落结构，增加土壤中拮抗细菌的丰度，提高三七的存苗率。生产上利用茴香与三七轮作对缓解连作障碍具有一定潜力。

The Effect and Mechanism of Fennel Crop Rotation on Soil Bacterial Community to Alleviate Replant Failure of Panax notoginseng

Panax notoginseng is a characteristic Chinese medicinal plant,but its cultivation was severely hampered by replant failure.Crop rotation is an effective measure to alleviate this problem.In this study,fennel was cultivated as the succeeding crop of P.notoginseng,and the rhizosphere soil of fennel was collected to make soil extract to assess the effect of fennel rotation on seedling survival rate and soil bacterial community of P.notoginseng.The seedlings survival rate was significantly increased by irrigating soil water extract from fennel rotation soil.In addition,the soil bacterial community was significantly changed with the increasing of richness index.At phylum level,the dominant phylum with relative abundance>1%,Proteobacteria and Actinobacteria,were significantly enriched.At genus level,the relative abundances of 66 genera were significantly increased and 30 genera were decreased.Among them,there are 14 dominant genera(the relative abundance was more than 0.2%)with significant increase and 8 dominant genera with significant decrease.In general,the number of increasing genera was more than that of decreasing genera.The dominant genera with significantly increased include the common antagonistic bacteria Pseudomonas and Bacillus.One strain of Bacillus and two strains of Pseudomonas isolated from the rhizosphere soil of fennel exhibited strong antagonistic activity to root rot pathogens Fusarium solani and Monographella cucumerina.In general,crop rotation of fennel can increase the seedlings survival rate of P.notoginseng and enrich the abundance of antagonism bacteria in bacterial community.It is potential to alleviate replant failure of P.notoginseng by rotation of fennel and P.notoginseng.