The impact of Lavandula stoechas L. degradation on arbuscular mycorrhizal fungi, in a Mediterranean ecosystem

Several studies have attempted to clarify the effect of plant essential oils on microorganisms in vitro. The specificity of mycorrhizas lies in the fact that it must be carried out in vivo. The aim of this study was to explore the effect of aromatic Lavandula stoechas L. degradation on development of two mycorrhizal species Septoglomus deserticola and Rhizophagus intraradices. The response of fungi colonization and host growth were monitored under different concentrations of L. stoechas leaves and essential oil. The major compounds of L. stoechas essential oil were fenchone (47.2%) and 1,8-cineole (14.3%). S. deserticola and R. intraradices colonized successfully the host plants. The plants growth was positively influenced after fungi inoculation. The addition of L. stoechas leaves-flowers in the soil altered mycorrhiza levels. Small amount of L. stoechas leaves-flowers (up to 2 g L-1) or L. stoechas essential oil (up to 25 mg L-1) was beneficial for fungi colonization. The level of inhibition was positively correlated with the added amount of aromatic plant in the soil. Inhibition was recorded in concentrations over 25 mg L-1 (essential oil/soil). It is suggested in soils that have accumulated a large amount of L. stoechas litter, to remove part of it avoiding mycorrhiza inhibition.