连作木薯对根际与非根际土壤真菌群落结构演替的影响

Effects of continuous cropping on fungal community structure succession in rhizosphere and non-rhizosphere soils of cassava

关键词:  木薯, 连作, 真菌, 根际与非根际土壤, 微生物多样性

Key words:  cassava(Manihot esculenta), continuous cropping, fungi, rhizosphere and non-rhizosphere soils, microbial diversity

摘要:

为揭示木薯连作障碍形成机制,该研究以定点大田连作木薯三年,利用高通量测序技术和生物信息学手段研究连作年限对木薯根际与非根际土壤真菌群落结构演替的影响。结果表明:(1)连作对木薯根际与非根际土壤真菌群落α多样性及β多样性影响显著。(2)木薯的主要优势菌门为子囊菌门、SAR超类群、担子菌门、毛霉门和unclassified_k_Fungi,主要优势菌纲为粪壳菌纲、散囊菌纲、座囊菌纲。非根际土壤中,子囊菌门组成变化较大,从第一年的漆斑菌属、粪壳菌纲、座囊菌纲向单一的Knufia属演化; 根际土壤的真菌则从子囊菌门的肉座菌目、刺盾炱目、漆斑菌属、座囊菌纲、粪壳菌纲向领鞭毛虫门Monosiga属演化。(3)土壤pH、有机质含量、碱解氮含量、有效磷含量、速效钾含量、脲酶活性对土壤真菌群落结构影响显著,尤其影响子囊菌门、SAR超类群、担子菌门和毛霉门的分布。综上认为,木薯连作会引起根系分泌物累积,改变土壤理化性质及真菌的生存环境,进而引起根际与非根际土壤真菌群落多样性和丰富度的变化。其中,非根际土壤中子囊菌由漆斑菌属、粪壳菌纲、座囊菌纲向单一的Knufia属演变; 根际土壤中子囊菌门的肉座菌目、漆斑菌属、粪壳菌纲等有益真菌的相对丰度随连作年限的增加而降低,进而引发木薯连作障碍。

Abstract:

For revealing the mechanism of cassava continuous cropping obstacle formation, we study planted cassava in a fixed field for three continous years, and applied high-throughput sequencing technology and bioinformatics to explore effects of continuous cropping on fungal community structure of both rhizosphere and non-rhizosphere soils of cassava. The results were as follows:(1)Continuous cropping caused significant effects on the α diversity and β diversity of rhizosphere and non-rhizosphere soil fungal communities of cassava.(2)The dominant fungi phyla of cassava rhizosphere and non-rhizosphere soils were Ascomycota, SAR_k_norank, Basidiomycota, Mucoromycota, and unclassified _k_Fungi, and the main classes were Sordariomycetes, Eurotiomycetes, and Dothideomycetes. The composition of Ascomycota of the non-rhizosphere soil varied with the continuous cropping years significantly and the Myrothecium, Sordariomycetes, and Dothideomycetes evolved to single genus Knufia in the first year. In the rhizosphere soil, Hypocreales, Chaetothyriales, Myrothecium, Dothideomycetes, and Sordariomycetes evolved to Monosiga, Choanoflagellida.(3)Soil pH, organic matter content, available nitrogen content, available phosphorus content, available potassium content, and urease activity significantly influenced the structure of fungal communities, especially for distributions of Ascomycota, SAR_k_norank, Basidiomycota, and Mucoromycota. In conclusion, continuous cropping of cassava influenced soil physicochemical properties through the accumulation of root exudates, thus altering the survival environment of fungi, leading to differences of the diversity and the abundance of fungal communities between cassava rhizosphere and non-rhizosphere soils. The ascomycetes in the non-rhizosphere soil evolved from Myrothecium, Sordariomycetes, and Dothideomycetes to single genus Knufia. The relative abundance of Hypocreales, Myrothecium, and Sordariomycetes of Ascomycota decreased with continuous cropping years in the rhizosphere soil, which may be one of main causes of the continuous cropping obstacles of cassava.