The experiment was conducted in a 'shade'-type greenhouse with 30% shade at the Instituto de Investigaciones Agropecuarias y Forestales (IIAF), Universidad Michoacana de San Nicolas de Hidalgo (UMSNH), Morelia, Michoacan, Mexico. Maximum and minimum temperatures in the greenhouse varied between 28 and 32 ℃ and between 8 and 18 ℃ respectively. Plants of the strawberry cultivar 'Aromas' were used that had previously been grown in a sterilised (95 ℃ water/steam, 40 min) substrate of coconut fibre/perlite (1:3 v/v) under greenhouse conditions. Before the experiment was established, the absence of AMF in the roots was verified by the ink and vinegar technique, modifying the duration of immersion in KOH and ink/vinegar solution (7 and 5 min respectively). Before planting, roots were disinfected by submerging them for 20 s in 20 g/L sodium hypochlorite solution and rinsing them in water. The inoculum was prepared with spores of Glomus intraradices cultivated in liquid medium (3.5 × 10⁶ spores/L, 90% viability; Premier Tech Biotechnologies Company, Quebec, Canada), which was diluted with fitagel (Sigma P-8169, Saint Louis, MO, USA) solution at 50 g/L to obtain a final concentration of about 5 × 10⁴ spores/L. The viability of spores was determined according to the method of An and Hendrix. Eighteen days after setting up the experiment, each plant received 2 mL of inoculum applied directly to the recently formed roots. One month later, after staining, the percentage of root colonisation was determined by the gridline intersect method. The experiment was organised as a full factorial, completely randomised design with two factors: inoculation (two levels: mycorrhizal and non-mycorrhizal plants) and N concentration in the nutrient solution (three levels: 3, 6 and 18 mmol/L). The six treatments were replicated four times, producing 24 experimental units with ten plants each. Every second day, all plants were irrigated up to substrate saturation. Nitrogen was supplied as NO and the cation/anion ratio was kept constant by varying the concentration of SO. When N was below 18 mmol/L, the cation concentrations were maintained as follows: K+, 3; Ca²⁺, 3.5; Mg²⁺, 1.5 mmol/L. They were increased in the 18 mmol/L N treatment: K+, 6.5; Ca²⁺, 7.5; Mg²⁺, 3.25 mmol/L. In all nutrient solutions the concentration of phosphorus (P) was 0.3 mmol/L. The other nutrients in the solutions were: H₃BO₃, 20; CuSO₄. 5H₂O, 0.5; Fe-EDTA (Ethylenediaminetetraacetic acid iron (III) sodium salt), 15; MnSO₄.H₂O, 12; (NH₄)₆Mo₇O₂₄ . 4H₂O, 0.05; ZnSO₄ . 7H₂O, 3 µmol/L. The pH was adjusted to 5.5 at every application date.

Mycorrhization did not modify the weight, diameter or length of strawberry fruits but had a negative effect on most colour parameters. Moreover, fruits of mycorrhizal plants had higher K and Cu concentrations and showed greater accumulation of most phenolic compounds.