Ergosterol as an Indicator of Endophyte Biomass in Grass Tissue

Abstract

Endophytic fungi of cool-season grasses grow primarily in the intercellular spaces of the grass leaf sheath and the aleurone layer of infected seed (Hinton and Bacon, I 985). Because this association is completely endophytic, and therefore inaccessible, the growth and physiology of endophytes in planta is poorly understood. Microscopic analysis of sectioned and stained tissues remains the primary method for the identification and quantitation of hyphae in infected grass leaves (Bacon, 1992; Breen, 1992). Unfortunately, these methods are tedious and not suitable for routine work. Biochemical markers such as glucosamine, extracellular lacase and adenosine 5′- triphosphate have been used to quantitate fungal biomass in other complex materials (Matcham et al., 1985; Suberkropp et al., 1993), but these methods also have disadvantages such as poor reproducibility and the potential interference from compounds in the plant tissue itself.