Open Access Research

A spectroscopy approach to the study of virus infection in the endophytic fungus Epichloë festucae

Cristina Petisco*, Balbino Garcia-Criado, Iñigo Zabalgogeazcoa, Beatriz R Vázquez-de-Aldana and Antonia Garcia-Ciudad*

Author Affiliations

Instituto de Recursos Naturales y Agrobiología de Salamanca, IRNASA-CSIC, Apdo. 257, 37071 Salamanca, Spain

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Virology Journal 2011, 8:286  doi:10.1186/1743-422X-8-286

Published: 8 June 2011

Abstract

Background

In this work we propose a rapid method based on visible and near-infrared (Vis-NIR) spectroscopy to determine the occurrence of double-stranded RNA (dsRNA) viruses in Epichloë festucae strains isolated from Festuca rubra plants. In addition, we examined the incidence of infections by E. festucae in populations of F. rubra collected in natural grasslands of Western Spain.

Methods

Vis-NIR spectra (400-2498 nm) from 124 virus-infected and virus-free E. festucae isolates were recorded directly from ground and freeze-dried mycelium. To estimate how well the spectra for uninfected and infected fungal samples could be differentiated, we used partial least-squares discriminant analysis (PLS1-DA) and several data pre-treatments to develop calibration models.

Results

Applying the best regression model, obtained with two sampling years and using standard normal variate (SNV) combined with first derivative transformation to a new validating data set (42 samples), we obtained a correct classification for 75% of the uninfected isolates and up to 86% of the infected isolates.

Conclusions

The results obtained suggest that Vis-NIR spectroscopy is a promising technology for detection of viral infections in fungal samples when an alternative faster approach is desirable. It provides a tool adequately exact and more time- and cost-saving than the conventional reference analysis.

Keywords:
Near-infrared spectroscopy; viruses; fungal endophytes; Epichloë festucae; Festuca rubra