Abstract
BackgroundIn 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.MethodsVis-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.ResultsApplying 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.ConclusionsThe 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.
Highlights
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 viruses in Epichloë festucae strains isolated from Festuca rubra plants
The perennial grass Festuca rubra is very common in semiarid grasslands of Western Spain, and wild populations of this species are often infected by the endophytic fungus Epichloë festucae [1,2]
Endophytic infection in populations of F. rubra and incidence of viruses in E. festucae In the six populations analyzed in 2008 we found that an average of 59% of the plants was infected by E. festucae
Summary
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. We examined the incidence of infections by E. festucae in populations of F. rubra collected in natural grasslands of Western Spain. The perennial grass Festuca rubra is very common in semiarid grasslands of Western Spain, and wild populations of this species are often infected by the endophytic fungus Epichloë festucae [1,2]. In populations of F. rubra infected by E. festucae, most plants are asymptomatic and produce infected seeds, a few plants may develop fungal stromata which block the emergence of flowering stems [3]. The associations between fungal viruses and their hosts are similar to plant-endophyte associations, because many known fungal viruses cause no obvious symptoms [5,6]. Totiviridae), and EfV2 is thought to be a member of the Narnaviridae family Both viruses are efficiently transmitted to asexual spores produced by infected isolates of the fungal endophyte. No obvious phenotype is observed in virus infected isolates of E. festucae [8,9]
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