Effect of particle size and spectral sub-range within the UV-VIS-NIR range using diffuse reflectance spectra on multivariate models in evaluating the severity of fusariosis in ground wheat

Control (crops grown in natural conditions) and Fusarium head blight (FHB) damaged (crops inoculated with Fusarium culmorum conidia) grain of four wheat cultivars was ground and sieved into three fractions of different particle size. A series of blended samples differing in content of damaged material were prepared within fractions and cultivars, and diffuse reflectance spectra recorded within the 200-2500 nm wavelength range. Partial least-squares (PLS) models for the percentage of damaged material in blended samples were built for each of twelve series within different spectral ranges, and the root-mean-squared error of cross-validation (RMSECV) was used for the assessment of model performance. Errors using the models were lowest for the finest fraction independent of spectral range; however, their values depended on the cultivar. RMSECV for the finest fraction averaged over cultivars ranged from a little below 3.0 (when the ultraviolet light sub-range was used or participated with another one) to 8.1% (when only the near infrared (NIR) sub-range was used). For the medium and coarse fractions, averaged errors showed the same tendency of dependence on the sub-range(s); however, with higher values that increased with an increase in particle size. In conclusion, within the different fractions of particle size and spectral ranges, the most sensitive to the presence of damaged material were models developed for the finest fraction and when the ultraviolet light sub-range was used in modelling.