Figure 4.

Three-dimensional slice maps of the correlation coefficients (R²) for the relationships between the yellow rust disease index and the new indices calculated from all possible three-band combinations at 3 nm band sampling intervals from the wavelengths sensitive in the different growth stages. (a) and (b) R² of PRI (λ1, λ2, λ3) (Photochemical Reflectance Index) at the early-mid and mid-late growth stages, respectively; (c) and (d) R² of ARI (λ1, λ2, λ3) (Anthocyanin Reflectance Index) at the early-mid and mid-late growth stages, respectively; λ1, λ2, and λ3 are the wavelengths sensitive to yellow rust discrimination.