24-Methyl/methylene sterols increase in monoxenic roots after colonization by arbuscular mycorrhizal fungi.

Characteristic sterols of transformed carrot (Daucus carota) and chicory (Cichorium intybus) roots colonized by different strains of arbuscular mycorrhizal (AM) fungi were identified. Sterols were extracted, analysed and identified by gas chromatography/mass spectrometry (GC-MS) from monoxenic cultures of mycorrhizal and nonmycorrhizal roots. After colonization by Glomus intraradices, Glomus proliferum and Glomus sp., carrot and chicory roots exhibited a significantly higher 24-methyl/methylene sterol content. A correlation was established between the content of the sum of 24-methyl cholesterol, 24-methylene cholesterol and 24-methyl desmosterol. This study clearly established that the increment of these characteristic sterols is an appropriate indicator of colonization by AM fungi of transformed roots. Metabolic origin and specificity of these sterols in mycorrhizal roots was researched. The 24-methyl/methylene sterol increase was observed only when the interaction between fungus and plant was completely established and the fungus was present inside the roots. [ABSTRACT FROM AUTHOR]