Levels and tissue distribution of loline alkaloids in endophyte-infected Festuca pratensis

Abstract

Festuca pratensis (meadow fescue) infected with the endophyte Acremonium uncinatum produces loline alkaloids (1-aminopyrrolizidines) that are not found in the uninfected grass or the fungus alone. Five alkaloids were identified by capillary GC and GC-MS: N-formylloline as the major compound, followed by N-acetylloline, N-acetylnorloline and trace amounts of loline and N-methylloline. A routine procedure for the extraction and sensitive quantitative analysis of loline alkaloids by capillary GC is described. The loline alkaloid levels and concentrations were followed quantitatively over the growing season of the grass-endophyte association. A detailed analysis of the tissue distribution of the alkaloids is given. The total alkaloid level per plant increases from almost zero in early spring and reaches its highest level during seed maturation. It drops to almost zero with seed dispersal and stalk senescence but increases again during the subsequent period of vegetative growth in late summer. The highest alkaloid concentrations were found in young leaves in early spring, and in panicles (spikelets, seeds) and leaf pseudostems during the period of vegetative growth in late summer and autumn. During seed germination loline alkaloids are not degraded, however, a significant proportion (about 20%) are lost by leaching, mainly during seed imbibition. Within a seed the embryo was found to contain a two-fold higher alkaloid concentration than the remaining seed tissue.