Nitrogen availability drives the effect of Glomus intraradices on the growth of strawberry (Fragaria x ananassa Duch.) plants.

BACKGROUND On the one hand, the critical nitrogen (N) content curve allows the minimal N content necessary for maximum growth rate at any stage of crop development to be predicted. On the other hand, arbuscular mycorrhizal fungi (AMF) transfer N from the soil to the plants and its growth and activity depends on the availability of soil N. Our objective was to investigate how the availability of N in the soil affects growth and the accumulation of N in inoculated strawberry plants. Root colonisation, dry matter accumulation and the critical N% curve were studied during growth of inoculated and non-inoculated strawberry plants grown at several N levels. RESULTS (1) The increase in the availability of N augmented root colonisation by AMF. (2) The effect of AMF on plant growth depended on N availability and the plant developmental status. (3) The critical %N curves were fitted by the following equations: %N = 2.81× (DM)(-0.21) (r² = 0.81) and %N = 2.89× (DM)(-0.32) (r² = 0.80) for inoculated and non-inoculated plants, respectively (where DM is the weight of leaf dry matter, in g plant⁻¹). CONCLUSION N availability was a key factor for root colonisation by AMF and for its contribution to plant growth. The patterns of the critical %N curves suggest that AMF modified the photosynthetic N use efficiency.