Abstract
A controlled environment experiment was conducted to determine the influence of defoliation on the regrowth and development of two tall fescue ( 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 and 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 DN11 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 DN11 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×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.
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