Plants control the structure of mycorrhizal and pathogenic fungal communities in soil in a 50-year maize monoculture experiment

Abstract

Abstract Aims Saprotrophic soil fungi participate in biomass mineralization, inhibit pathogen development and promote plant growth. Pathogens accumulate in soil and decrease crop yields. The structure of fungal communities is determined mainly by the organic matter content and pH of soil. Little is known about the influence of crop rotation and long-term monoculture on saprotrophic fungi that decompose plant roots and crop residues as sources of soil biomass. Methods Fungal communities that promote plant growth (arbuscular mycorrhizal fungi (AMF), yeasts, Trichoderma spp.), cellulolytic fungi and pathogenic species were analyzed in a 6-year crop rotation system (maize – spring barley – peas – winter rapeseed – winter wheat – sugar beets) and in 50-year maize monoculture. Fungal DNA was extracted from the rhizosphere and plant roots, and the ITS2 region of fungal rDNA was analyzed by high-throughput sequencing. In both treatments, weeds were controlled chemically (terbuthylazine + mesotrione + s-metolachlor) or mechanically. Results A total of 311 fungal species were identified. The biodiversity of soil fungi, in particular AMF and yeasts, was higher in monoculture than in crop rotation. Maize pathogens were more frequently identified in monoculture, whereas species of the genus Trichoderma were more prevalent in crop rotation. Herbicides clearly increased the abundance of cellulolytic fungi of the phyla Mucoromycota and Mortierellomycota, Mortierella spp. and Minimedusa polyspora. The abiotic properties of soil were affected by the cropping sequence. The content of organic carbon (Corg) and the availability of P and Mg decreased in monoculture. Maize yields were bound by a strong positive correlation with the availability of macronutrients and Corg in soil, as well as a weak positive correlation with the abundance of Trichoderma spp., Mucoromycota and Mortierellomycota. Conclusions Fungi exert a complex and ambiguous effect on maize biomass yields, whereas a decrease in the macronutrient content of soil in monoculture strongly decreases maize yields. In the long term, the cropping sequence considerably influences the structure of the soil microbiome which can be a reservoir of unique species and species that minimize the negative effects of monoculture in agroecosystems. Graphical Abstract