Temporal variation of the molecular diversity of arbuscular mycorrhizal communities in three different winter cover crop rotational systems

Abstract

A clear understanding of the significance of arbuscular mycorrhizal fungi (AMF) to phosphorus (P) nutrition in intensively managed cover crop rotational systems with soybean [Glycine max (L.) Merr.] will impact how we currently manage these systems, particularly crop rotation decisions. We investigated the impact of wheat (Triticum aestivum L.), rapeseed (Brassica napus L.), or fallow on composition of AMF communities in soil over 2 years of a consecutive soybean rotational system. The composition of AMF communities was characterized on the basis of the large subunit (LSU) ribosomal DNA (rDNA). AMF spore abundance in soil after cultivation of wheat was higher than that after rapeseed or fallow for the all sampling years. Phylogenetic analysis identified 19 AMF phylotypes, including five Glomus; three Gigaspora; two of Acaulospora, Funneliformis, and Rhizophagus; one of Racocetra, Claroideoglomus, Diversispora, and Sclerocystis; and an unknown glomeromycete in soil. Dominant phylotypes of Glomerales occurred widely across the winter cover crop rotations. However, the phylotype richness and diversity of AMF communities were unchanged among crop rotations and years. Redundancy analysis (RDA) demonstrated that AMF communities within a crop rotation were not significantly different. However, when analyzed over a 2-year period, the composition of AMF communities was clearly influenced by year where the distribution of specific AMF phylotypes responded to the winter cover crop management. Thus, diversity of AMF communities in soil was clearly shifted by rotation year, which indicated that other abiotic environmental factors may impact composition AMF communities more than winter cover crop rotational systems.