Identification of a Unique Spectral Signature of Black Layer Formation in Maize (Zea mays L.).

Physiological maturity in maize is reached at the developmental stage black layer, where photosynthates are no longer able to move into the developing kernels. Currently, there is no high-throughput field-based phenotyping (FBP) method available for detecting black layer, although remotely sensed spectral data may offer a solution to this problem. The aim of this project is to identify a unique reflectance signature associated with physiological maturity in maize that is robust. Being repeatable across genotypes, different environmental conditions, different senescence patterns, etc., is essential. Several types of remotely sensed data have been used including hyperspectral data generated with a dual-channel UniSpec and an unmanned aerial vehicle (UAV) mounted multispectral camera. Accompanying the remotely sensed data are ground-truthed data consisting of visual determination of black layer and SPAD readings.

Initial experiments consisted of two planting dates at one location and involved four short-season hybrids that exhibited two different senescence patterns at maturity, a rapid “die and dry” phenotype and an extended “stay green” phenotype. The hybrids differed in the accumulation of anthocyanins in the leaf tissues, shown by visual photography and vegetative index analysis. We have tentatively identified a region of the spectrum that exhibits a change as black layer approaches. This region is consistent across the four genotypes and the two planting dates. To confirm our initial findings we are now examining additional genotypes and adding a second growing season to the data set.