Canopy roughness: a new phenotypic trait to estimate above-ground biomass from unmanned aerial system

• Herrero-Huerta, M., Bucksch, A., and Rainey, K. (2020) 'Canopy roughness: a new phenotypic trait to estimate above-ground biomass from unmanned aerial system'. Plant Phenomics. In Press. Article ID 6735967

Cost-effective phenotyping methods are urgently needed to advance crop genetics in order to meet the food, fuel and fiber demands of the coming decades. Concretely, characterizing plot level traits in fields are of particular interest. Recent developments in high-resolution imaging sensors for UAS (unmanned aerial systems) focused on collecting detailed phenotypic measurements are a potential solution. We introduce canopy roughness as a new plant plot-level trait. We tested its usability with soybean by optical data collected from UAS to estimate biomass.

We validate canopy roughness on a panel of 108 soybean [Glycine max (L.) Merr.] recombinant inbred lines in a multi-environment trial during the R2 growth stage. A SenseFly eBee UAS platform obtained aerial images with senseFly S.O.D.A. compact digital camera. Using a structure from motion (SfM) technique, we reconstructed 3D point clouds of the soybean experiment. A novel pipeline for feature extraction were developed to compute canopy roughness from point clouds. We used regression analysis to correlate canopy roughness with field-measured aboveground biomass (AGB) with a leave-one-out cross-validation.

Overall, our models achieved a coefficient of determination (R2) greater than 0.5 in all trials. Moreover, we found that canopy roughness has the ability to discern AGB variations among different genotypes.

Our test trials demonstrate the potential of canopy roughness as a reliable trait for high-throughput phenotyping to estimate AGB. As such, canopy roughness provides practical information to breeders in order to select phenotypes on the basis of UAS data.