Impact of a 5-year winter cover crop rotational system on the molecular diversity of arbuscular mycorrhizal fungi colonizing roots of subsequent soybean

The impact of winter cover crops, specifically wheat (Triticum aestivum L.), red clover (Trifolium pratense L.), and rapeseed (Brassica napus L.) or winter fallow, on community composition of arbuscular mycorrhizal fungi (AMF) in subsequent soybean roots was investigated in a 5-year field trial on andosolic soils in Japan. Soybean roots were sampled at full-flowering and analyzed for AMF communities using a partial LSU rDNA region. Phylogenetic analysis detected 22 AMF phylotypes, including eight Glomus, three Gigaspora, two Scutellospora, three Acaulospora, two Rhizophagus, and one of Funneliformis, Diversispora, Paraglomus, and an unknown glomeromycete in the roots. The 5-year rotation of different winter cover crops or winter fallow did not impact the molecular diversity of AMF communities colonizing the roots of subsequent soybean. In all of the rotations, Glomus and Gigaspora phylotypes were common to soybean roots over the 5-year period. Redundancy analysis (RDA) demonstrated that AMF communities in the roots of subsequent soybean were not significantly different among winter cover crop rotations or fallow. However, AMF communities in soybean roots were clearly influenced by rotation year suggesting that climate or other environmental factors were more important than winter cover cropping system management.