Effects of cutting frequency and height on alkaloid production in endophyte-infected drunken horse grass (Achnatherum inebrians).

An evaluation was performed on the influence of mowing height (2.5, 5.0 or 7.5 cm) and mowing frequency (weekly or fortnightly) on levels of ergot alkaloids (ergine and ergonovine) formed in drunken horse grass, Achnatherum inebrians, grown under greenhouse conditions. Samples were taken monthly and alkaloids were extracted and analyzed by reverse-phase HPLC. Alkaloid levels increased more or less linearly with plant age over the first four months following establishment. Levels were higher in samples cut fortnightly compared to those cut weekly, and were higher when plants were cut at a mowing height of 7.5 cm vs. 2.5 cm. In most cases, the highest alkaloid levels observed were almost three times those of the lowest. If plant protection applications are developed for the endophytic fungus, Neotyphodium gansuense, it will be necessary to be aware of the potential role of plant husbandry practices (e.g., defoliation frequency and intensity) for reducing or enhancing levels of plant alkaloids. Similar husbandry factors may affect alkaloid levels in other Neotyphodium-grass associations, which would be interesting for further study.