Endophytic fungi of grasses in the genus Epichloë produce protective alkaloids that are known to deter herbivory. In addition to direct measurement of alkaloids, various feeding tests are used to assess bioactivity. Brine shrimp (Artemia salina) assays have been used to detect bioactivity in plants and fungi, including endophytic fungi of medicinal plants. We tested the utility of a brine shrimp assay to detect bioactivity in the endophyte-infected (symbiotic) grass Agrostis hyemalis. We exposed brine shrimp larvae (nauplii) to whole plant aqueous extracts as well as to fermentation cultures of the isolated fungus and observed nauplii survival after 24 hours. Whole plant extracts of symbiotic grasses reduced survival, compared to brine shrimp survival in the extracts of grass lacking the endophyte. Furthermore the effect of symbiotic grass extracts was dose-dependent, with reduced survival in the higher concentration compared to lower. These results suggest that the brine shrimp assay detects bioactivity of endophyte-produced toxins. This short-term assay is simple, inexpensive, requires no specialized equipment, is suitable for student research projects, and could potentially serve as an initial screening of symbiotic grasses for alkaloid production.

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