Potential role of arbuscular mycorrhizal fungi in the accumulation of polyphenols in Lamiaceae species

The aim of this study was to examine the effect of arbuscular mycorrhizal (AM) fungi colonization on the biomass and polyphenol content of two economically important Lamiaceae herbs. In this regard a 15-week pot experiment was performed under controlled conditions with Origanum majorana L. and Melissa officinalis L. applying a commercially available AM fungi mixture (Glomus etunicatum, Glomus claroideum, Rhizophagus intraradices) for inoculation. The efficiency of mycorrhization was determined [1,2]. The major polyphenols of the two plants were identified and quantified using HPLC-ESI-qTOFMS and HPLC-PDA systems [3]. From the aerial parts of the plants the major polyphenols were tentatively identified, five from marjoram (apigenin-6,8-di-C-glucoside, luteolin-7'-O-glucuronide, rosmarinic acid, apigenin-glucuronide, lithospermic acid A isomer,) and three from lemon balm (rosmarinic acid and two lithospermic acid A isomers). According to our results marjoram had higher level of fungal colonization compared to lemon balm. AM fungal inoculation significantly increased the biomass of marjoram, but did not cause differences in lemon balm yield. In the term of polyphenol content the mycorrhization mostly affected the accumulation of lithospermic acid A isomers and rosmarinic acid. The AM fungal colonization significantly increased the content of these compounds in lemon balm, but decreased in marjoram. Take in account the yield of biomass the total yield of polyphenols was increased as the result of mycorrhization in both plants. The results of the present study show that AMF can provide different services for each herb. For instance while marjoram benefits more from the AMF colonization in terms of growth, lemon balm has higher content of phenolic acids. It shows that the effect and outcome of mycorrhization depends on the plant and also the fungal species. Thus the application of optimized AM fungal inoculum could improve the quantity and quality of medicinal plant material.

Acknowledgements: Authors thank OTKA (PD105750) for the financial support.

Keywords: Origanum majorana, Melissa officinalis, arbuscular mycorrhizal fungi, polyphenol.

References:

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