Abstract
Near infrared spectroscopy (NIRS) is an accurate, fast and nondestructive technique whose use in predicting forage quality has become increasingly relevant in recent decades. Epichloë-infected grass varieties are commonly used in areas with high pest pressure due to their better performances compared to endophyte-free varieties. The insect resistance of Epichloë-infected grasses has been associated with four main groups of endophyte secondary metabolites: ergot alkaloids, indole-diterpenes, lolines and peramine. Concentrations of these alkaloids are usually measured with high performance liquid chromatography or gas chromatography analysis, which are accurate methods but relatively expensive and laborious. In this paper, we developed a rapid method based on NIRS to detect and quantify loline alkaloids in wild accessions of Schedonorus pratensis infected with the fungal endophyte Epichloë uncinata. The quantitative NIR equations obtained by modified partial least squares algorithm had coefficients of correlation of 0.90, 0.78, 0.85, 0.90 for N-acetylloline, N-acetylnorloline and N-formylloline and the sum of the three, respectively. The acquired NIR spectra were also used for developing an equation to predict in planta fungal biomass with a coefficient of correlation of 0.75. These results showed that the use of NIRS and chemometrics allows the quantification of loline alkaloids and mycelial biomass in a heterogeneous set of endophyte-infected meadow fescue samples.
Highlights
The physical, non-destructive technique of near-infrared spectroscopy (NIRS) has dramatically changed the analysis of very different materials, especially in agricultural and food industries [1]
TEhLeISaAi-mbaosefdthpisrowtoocrokl w[35a]s. tDoeesvpaitleuaatevatrhieetsyuoitfasbtirlaitteygoiefsN, qIuRasnptieficctartoioscnoopfyEfpoirchqluoëanmtyitcaetliivuemaninalysis of loleinxepearlikmaelontiadtsioannodr mpryaccetilciealinbitohemcaosnsteinxtmofefaodraogwe cfoemscpuaenpielsandtids innoftescpteredawd.ith the fungal endophyte E. uncinatTa.he aim of this work was to evaluate the suitability of NIR spectroscopy for quantitative analysis of loline alkaloids and mycelial biomass in meadow fescue plants infected with the fungal endophyte 2
The selection of the best NIRS equations for alkaloid quantification was based on the following statistical methods: (i) the multiple correlation coefficient (RSQ) which measures the fitting degree between predicted data and actual concentration; (ii) the Standard Error of Calibration (SEC), an estimate of the best accuracy obtainable using the specific wavelengths of the calibration equation; (iii) Residuals, differences between the actual value yi and the predicted value; (iv) BIAS, the medium value of the residuals; (v) the Standard Error of Cross Validation (SECV), and (vi) the ratio of standard deviation (SD) to standard error of cross-validation (SECV) of the data set, known as Ratio performance deviation (RPD) ratio which according to Williams and Sobering [43] is desired to be larger than 2.0 for good calibration
Summary
The physical, non-destructive technique of near-infrared spectroscopy (NIRS) has dramatically changed the analysis of very different materials, especially in agricultural and food industries [1]. Almost ten years later NIRS was first used to measure forage quality [6] and since became increasingly relevant to the extent that it is a routine analysis technique in forage research and breeding Most of these analyses predict aspects about forage composition in terms of chemical fractions such as crude protein, neutral-detergent fiber, acid-detergent fiber, water-soluble carbohydrates, lignin and dry-matter digestibility [6,7,8] and recently other parameters such as alkaloids [9]. Quantitative analysis of alkaloids is mostly based on high performance liquid chromatography (HPLC) and on gas chromatography [23,24,25] These methods allow high precision measurements, but they use relatively complicated protocols, expensive chemicals and instruments. UncinatTa.he aim of this work was to evaluate the suitability of NIR spectroscopy for quantitative analysis of loline alkaloids and mycelial biomass in meadow fescue plants infected with the fungal endophyte 2. F[3a8v]illfeoleltoawl.i[n3g5].Faville et al [35]
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