Ergosterol as an indicator of endophyte biomass in grass seeds

Ergosterol can be used as a marker to estimate fungal biomass in soil and plant-fungal tissue samples. The following experiments assess the application of ergosterol analysis to endophyte determinations in grass seeds. Ergosterol was present in all endophytic fungi tested, ranging from 185.2 mu g g(-1) in Epichloe typhina to 1225.5 mu g g(-1) in Neotyphodium lolii. Significant differences in ergosterol content occurred both between and within species of endophytic fungi. Ergosterol content of grass seeds was highly correlated (r(2) = 0.99) to the endophyte content of the seeds. Several extraction techniques were tested and found to yield variable results, but the method that gave the most complete extraction in seeds was methanol extraction under refluxing conditions. The endophyte content of fine fescue seed samples was predicted from ergosterol analysis and found to be well-correlated with microscopic analysis. It is concluded that ergosterol analysis can be used in both diagnostic and research applications to predict endophyte content in seed samples.