Fig. 1. Schematic diagram of chlorophyll fluorescence spectrum

Fig. 2. Fluorescence spectra of normal leaves, mild disease stage and severe disease stage

Fig. 3. The first three PCs score plots of spectra of all cultivars

Fig. 4. Partial least squares discrimination model
(a): PLS-DA calibration model; (b): PLS-DA prediction model

Fig. 5. Support vector machine prediction model with different kernel functions
(a): RBF-Kernel prediction model; (b): LIN-Kernel prediction model;(c): Polynomial-Kernel prediction model; (d): Sigmoid-Kernel prediction model

Fig. 6. Principal component contribution rate distribution

Fig. 7. PCA-LDA prediction model