Arbuscular mycorrhizal fungus-induced changes in the accumulation of secondary compounds in barley roots

Hordeum vulgare (barley) was grown in a defined nutritional medium with and without the arbuscular mycorrhizal fungus Glomus intraradices. HPLC of methanolic extracts from the roots of mycorrhized and non-mycorrhized plants revealed fungus-induced accumulation of some secondary metabolites. These compounds were isolated and identified by spectroscopic methods (NMR, MS) to be the hydroxycinnamic acid amides N-(E)-4-coumaroylputrescine, N-(E)-feruloylputrescine, N-(E)-4-coumaroylagmatine and N-(E)-feruloylagmatine, exhibiting a transient accumulation, and the cyclohexenone derivative 4-(3-O-beta-glucopyranosylbutyl-3-(hydroxymethyl)-5,5-dimethyl-2-cyclohexen-1-one and 4-{3-O-[2'-O-beta-glucuronosyl)-beta-glucopyranosyl]-butyl}- 3,5,5-trimethyl-2-cyclohexen-1-one (blumenin), exhibiting a continuous accumulation. A third cyclohexenone derivative, 4-{3-O-[(2'-O-beta-glucuronosyl)-beta-glucopyranosyl]-1-butenyl}-3,5,5-trimethyl-2-cyclohexen-1-one, was detectable only in minute amounts. It is suggested that accumulation of the amides in early developmental stages of barley mycorrhization reflects initiation of a defence response. However, the continuous accumulation of the cyclohexenone derivatives. especially blumenin, seems to correlate with the establishment of a functional barley mycorrhiza. Copyright (C) 1997 Elsevier Science Ltd.