Figure 2. Phenotypic and genetic correlation coefficients between different spectral reflectance indices (mean of different growth stages across year/location) and grain yield (mean of two locations in Exp-1 and 2 yr in Exp-2 and Exp-3). GNDVI, green normalized difference vegetation index; NWI-1, normalized water index 1; NWI-2, normalized water index 2; NWI-3, normalized water index 3; NWI-4, normalized water index 4; RNDVI, red normalized difference vegetation index; SR, simple ratio; WI, water index.