Defoliation and leaf age influence on ergot alkaloids in tall fescue

Abstract

A controlled environment experiment was conducted to determine the influence of defoliation on the regrowth and development of two tall rescue (Festuca arundinacea Schreb) host-endophyte (Neotyphodium coenophialum Morgan-Jones and Gams (Glenn. Bacon. Price and Hanlin comb. nov) associations (DN2 and DN11), known to differ in morphology trod alkaloid production capacity. Defoliation treatments included an uncut control, and clipping to a 5- or 10-cm residue height. In a separate experiment, leaf age effects were determined on an uncut plant canopy. Ergot alkaloid concentration was greatest in pseudostem and least in harvested leaf. Non-infected plants were devoid of alkaloid. Alkaloid production (expressed as a function of dry matter) and yield were greater in uncut than clipped plants, and were greater in DN1] than DN2 plants. Alkaloid production increased with increasing N concentration in both associations; however, the rate of production was influenced by concentration of non-structural carbohydrate. Leaf age influenced leaf mass and alkaloid concentration and yield. Oldest leaves (>6 weeks after appearance) of DN2 and DN 11 had the lowest concentrations of ergot alkaloid, while leaves that were 2 to 4 weeks old had the greatest alkaloid concentration and yield (alkaloid concentration x leaf mass). Repeated defoliation reduced the production of alkaloids, but did so as a function of non-structural carbohydrate. Our data suggest that alkaloid production can be modified by defoliation as well as by host-endophyte association.