Azoxystrobin alters the dynamics of short-term phosphorus uptake of mycorrhizal potato plants associated to Rhizophagus irregularis

Rodriguez-Morelos, Victor Hugo [UCL] Declerck, Stephan [UCL] Calonne, Maryline [UCL]

Background: Azoxystrobin is widely used in crops against several fungal diseases, but may have potential negative effects on soil microorganisms beneficial to plants such as arbuscular mycorrhizal (AM) fungi. To date, the impact of azoxystrobin has been studied on the growth and healing capacity of AM fungi, but not on the inorganic phosphorus (Pi) uptake dynamics. Aims: The aim of the study was to investigate the impact of azoxystrobin on the dynamics of Pi uptake by potato plants associated or not to Rhizophagus irregularis. Additionally, fungal root colonization, plant growth and P accumulation were assessed. Methods: A semi-hydroponic cultivation system was used using mycorrhizal (M) and nonmycorrhizal (NM) plants growing in presence/absence of azoxystrobin. The percentage of Pi depletion in the nutrient solution was determined by inductive coupled plasma atomic emission spectrometer after 30 and 60 days of circulation. Results: Whatever the presence/absence of the AM fungus, azoxystrobin decreased Pi uptake by plants after 30 days of growth. Conversely, after 60 days in absence of azoxystrobin, a larger Pi uptake was measured in the M plants, while the reverse was noticed in presence of azoxystrobin. Conclusions: The M plants were more affected by azoxystrobin than those growing in absence of the fungicide, suggesting a direct effect of azoxystrobin on the AM fungus and an indirect effect on the plant-fungus associates via a potential imbalance in the transfer of nutrients. Although it is difficult to extrapolate our results to field, fungicide toxicity on crops inoculated with selected AM fungi deserve to be explored.