Evaluation of Genetic Gain for Dynamic Leaf Traits in Maize Using Field Spectroscopy.

New technology must be utilized in order to continue pushing for genetic gains in the breeding industry. Nondestructive, high-throughput spectrometer measurements can be taken throughout the growing season to monitor various physiological and morphological traits in order to identify productive cultivars. As a result, a set of 36 era hybrids – popular commercial maize hybrids grown from 1936 to 2012 – were used to display the genetic gain of various traits and hyperspectral reflectance indices. Along with an increased grain yield of 76 kg/ha/yr, modern hybrids exhibited decreased plant and ear height, root and stalk lodging, senescence, and anthesis-silking intervals, and increased leaf relative water and chlorophyll contents. The 760/730 reflectance index correlated well with leaf chlorophyll and water contents (R² values of 0.65 and 0.43, respectively). The index primarily served as a proxy for leaf chlorophyll content; in turn, gross primary production. At many of the measurement dates throughout the season (V10 – R6), the index captured significant genetic gain. However, the peak gains in index values (determined by regression slopes) surrounded flowering. Therefore, the 760/730 index is robust at differentiating hybrids based on their year of release and suggests that modern hybrid leaf physiology is most distinct around anthesis.