The effects of laurel (Laurus nobilis L.) on development of two mycorrhizal fungi

Hundreds of aromatic plant species are growing naturally around Mediterranean. Plant essential oils are incorporated in aromatic plant material and follow the litter fall. During litter degradation, the presence of essential oils can affect soil microorganisms. Mycorrhizal fungi have never been investigated so far under the presence of volatile oils. The aim of this study was to explore the effect of aromatic Laurus nobilis L on development of two mycorrhizal species Glomus deserticola and Glomus intraradices. The response of fungi colonization and host growth were monitored under different concentrations of L nobilis leaves and essential oil. The major compounds of L nobilis essential oil were 1,8-cineole (49.6%), sabinene (7.8%), alpha-pinene (6.0%), eugenole (5.6%), alpha-terpinyl acetate (5.2%) and beta-pinene (5.1%). Both mycorrhizal fungi colonized successfully the host plants whose growth was positively influenced by mycorrhizal fungi. G. deserticola presented higher infection level than G. intraradices. The addition of L nobilis leaves in the soil resulted in mycorrhiza inhibition. The level of inhibition was positively correlated with the added amount of aromatic leaves in the soil. The essential oil presented a little higher inhibition than the leaves. The presence of this aromatic plant in many different ecosystems could contribute in mycorrhiza inhibition and it is suggested, when it's possible, reduction of laurel litter before reforestation programs. (C) 2011 Elsevier Ltd. All rights reserved.