Spectral correlation between wheat genotype replications over the visible and near-infrared spectrum

The growth stage best suitable for wheat yield phenotyping has been a hot topic. This study provides a fresh insight into it, from the perspective of spectral correlation between wheat genotype replications. A number of 340 wheat genotypes and their replication were distributed in separate parts (west and east) of an experiment field (2019–2020) in Ashland, Kansas, USA. Unmanned aerial vehicle based hyperspectral images (400–100 nm) of the experiment field were taken over the late growing season, on 29 May 2020, 5 June 2020, and 12 June 2020, respectively. For each narrow spectral band, we calculated a coefficient of determination (R 2) between the reflectance of genotype replications. Results suggest that R 2 is relatively stable within visible spectrum (450–700 nm) and within near-infrared (NIR) spectrum (770–1000 nm), though it tends to be higher for the visible bands. Moreover, while the R 2 of the visible bands decreases across the three dates, it increases for the near-infrared bands. These findings suggest that genetic information is better reflected in visible reflectance than in near-infrared reflectance. Among the three dates, the one when highest intra-genotype spectral correlation over visible spectrum was observed might be the best timing to discriminate yield levels of different genotypes.