Abstract

The mid-infrared (MIR) response of cassava leaves (Manihot esculenta Crantz) at different ontogenetic stages and during postharvest deterioration was studied. For this, Fourier-transform mid-infrared spectroscopy (FT-MIR; 4000–600 cm−1) was used to identify spectral signatures and indices as spectral indicators of leaf development and physiological status. Cassava’s HMC-1 variety was used as the model. Spectral signatures were obtained from leaves at two phenological stages (4 and 6 months after planting) using FT-MIR spectroscopy with an attenuated total reflectance (ATR) accessory. A set of classical and experimental spectral indices based on contrast relationships were evaluated, and their discriminatory power across ontogeny was assessed using ANOVA/Kruskal–Wallis and post hoc tests. Postharvest deterioration effects were examined through postharvest monitoring (1–20 days), with temporal, ontogenetic, and interaction effects validated using linear mixed models (LMM), while multivariate structure and spectral convergence were explored via principal component analysis and hierarchical clustering (PCA-HCA). Functionally enhanced derivative spectroscopy (FEDS) was applied as a derivative-based spectral enhancement approach of FT-MIR; in addition, comparative analysis and spectral correlation mapping allowed signals’ selective enhancement and their association with structural molecular components. FEDS-based signal ratios (e.g., 3400/2920 and 1710/1640 cm−1) showed an adequate differentiation of mature leaves and were consistent with spectral changes commonly associated with tissue hydration and cuticular ester-related components. FT-MIR indices showed higher sensitivity to mature stages compared to other ontogenies. It is concluded that FEDS-improved FT-MIR allows the construction of consistent spectral signatures and an enhanced extraction of indices with potential as discriminatory spectral indicators of leaf maturation and postharvest deterioration in cassava.

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