An application of reflectance spectroscopy to differentiate of entomopathogenic fungi species

Abstract

Fourier Transform Infrared Spectroscopy (FTIR) methods are the most commonly used spectroscopic techniques for differentiation of fungi species, however reflectance spectroscopy as a non-invasive technique can also be used. The aim of the study was to develop a method to rapidly differentiate fungi by means of reflectance spectroscopy using visible-infrared spectrum. Spectral measurements were conducted on six entomopathogenic fungi: Beauveria bassiana, Isaria fumosorosea, I. farinosa, I. tenuipes, Lecanicillium lecanii, L. muscarium cultured on Petri-dishes. The FieldSpec3 ASD spectroradiometer. Recording reflected radiance in the range 350–2500 nm was used. Measurements were performed in two modes: contact and proximal and obtained spectra were transformed using two methods: Savitzky-Golay (SG) and baseline alignment (BA) smoothing and derivative. The success rate of 100% in differentiate between fungi species was achieved with spectra recorded in visible-near infrared range with contact and proximal measurement and after SG transformation. Two wavelengths (411 nm and 520 nm) were needed to differentiate fungi using SG and proximal measurement while seven wavelengths were necessary to get full separation with contact measurement. BA spectra transformation method gave separation accuracy of 84, and 90% with four to five wavelengths for contact and proximal measurements, respectively, however, BA do not require full spectrum of wavelengths to fungi discrimination. Proposed reflectance spectroscopy method could discriminate between fungi species very similar macroscopically e.g. L. lecanii and L. muscarium until recently recognized as one species.