Diversification of crops and intensification of canola impact the diversity, community structure, and productivity in successive crop systems: A study on arbuscular mycorrhizal fungal communities in roots and rhizosphere

The widespread cultivation of canola, conventionally still considered a non-host plant for AM fungi, coupled with its increasing frequency in crop rotations, raises concerns about its impacts on soil microbial diversity and overall crop productivity. The main objective of this study is to assess the influence of different crop succession systems, incorporating canola, on AM fungal diversity and community structure in both the roots and in the rhizosphere, as well as on productivity of each crop present within the succession. Doubling the frequency of canola occurrence in a 4-year crop succession did not reduce the productivity of the other crops in the succession, nor did it result in a decrease in AM fungal biodiversity in the roots or rhizosphere of these crops. Interestingly, the diversity of AM fungi was higher in canola roots compared to wheat roots, indicating that canola might serve as a rudimentary host of AM fungi. The succession systems did, however, alter the AM fungal community structure in both roots and rhizosphere environments, exhibiting positive or negative correlations with crop productivity. This suggests that a simple modification of the cropping system could potentially be employed to manipulate root or rhizosphere microbiomes. Results of this study add to the growing body of evidences that plants that were thought to be non-AM fungi host, such as plants from the Brassicaceae family, could in fact interact with AM fungi.