Jonathan Luetchens, Department of Agronomy and Horticulture, University of Nebraska - Lincoln, Lincoln, NE and Aaron J Lorenz, Agronomy and Plant Genetics, University of Minnesota, St. Paul, MN
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.