Quantification of Acremonium coenophialum in Tall Fescue Seed Using Near Infrared Reflectance Spectroscopy1

Abstract

Near infrared reflectance spectroscopy (NIRS) can be used to evaluate major feed quality components of forage. Our objective was to determine whether NIRS could measure a minor quality component, the endophyte (Acremonium coenophialum Morgan‐Jones and Gams) in tall fescue (Festuca arundinacea Schreb.) seed. Two‐hundred seed lots were assayed for endophyte content using two procedures: the enzyme‐linked immunosorbent assay (ELISA) and an aniline blue mycelium stain. From the 200 seed lots, 74 were selected to obtain an even distribution of sample numbers over a range of endophyte infection from zero to high. Calibration equations for predicting endophyte content were obtained by multiple linear regression of NIRS spectral data and laboratory values for each procedure from 56 of the 74 seed lots. Calibration equations were verified on the remaining 18 seed lots. Five wavelengths were necessary to obtain the best equations for endophyte concentrations for each laboratory assay. The squared correlation coefficients (R2) for the calibration equations were low for both assays (R2 = 0.53 and 0.74). Correlation coefficients for verification data were also low (r2 = 0.31 and 0.54). Adding the 18 verification samples to the calibration set increased r2 for the mycelium stain assay but decreased R2 for ELISA. We conclude that laboratory methods used to assay the endophyte in tall fescue seed do not have the precision and accuracy necessary to calibrate NIRS instrumentation for routine analysis.