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

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.