title: Application of unmanned aerial systems for high throughput phenotyping of large wheat breeding nurseries.
abstract: BACKGROUND
  Low cost unmanned aerial systems (UAS) have great potential for rapid proximal measurements of plants in agriculture. In the context of plant breeding and genetics, current approaches for phenotyping a large number of breeding lines under field conditions require substantial investments in time, cost, and labor. For field-based high-throughput phenotyping (HTP), UAS platforms can provide high-resolution measurements for small plot research, while enabling the rapid assessment of tens-of-thousands of field plots. The objective of this study was to complete a baseline assessment of the utility of UAS in assessment field trials as commonly implemented in wheat breeding programs. We developed a semi-automated image-processing pipeline to extract plot level data from UAS imagery. The image dataset was processed using a photogrammetric pipeline based on image orientation and radiometric calibration to produce orthomosaic images. We also examined the relationships between vegetation indices (VIs) extracted from high spatial resolution multispectral imagery collected with two different UAS systems (eBee Ag carrying MultiSpec 4C camera, and IRIS+ quadcopter carrying modified NIR Canon S100) and ground truth spectral data from hand-held spectroradiometer.
  
  
  RESULTS
  We found good correlation between the VIs obtained from UAS platforms and ground-truth measurements and observed high broad-sense heritability for VIs. We determined radiometric calibration methods developed for satellite imagery significantly improved the precision of VIs from the UAS. We observed VIs extracted from calibrated images of Canon S100 had a significantly higher correlation to the spectroradiometer (r = 0.76) than VIs from the MultiSpec 4C camera (r = 0.64). Their correlation to spectroradiometer readings was as high as or higher than repeated measurements with the spectroradiometer per se.
  
  
  CONCLUSIONS
  The approaches described here for UAS imaging and extraction of proximal sensing data enable collection of HTP measurements on the scale and with the precision needed for powerful selection tools in plant breeding. Low-cost UAS platforms have great potential for use as a selection tool in plant breeding programs. In the scope of tools development, the pipeline developed in this study can be effectively employed for other UAS and also other crops planted in breeding nurseries.
authors.affiliation: Department of Geography, Kansas State University, Manhattan, KS 66506 USA.
authors.forename: Atena
authors.initials: A
authors.lastname: Haghighattalab
authors.affiliation: International Maize and Wheat Improvement Center (CIMMYT), Int. Apdo., Postal 6-641, 06600 Mexico, D.F. Mexico.
authors.forename: Lorena
authors.initials: L
authors.lastname: González Pérez
authors.affiliation: International Maize and Wheat Improvement Center (CIMMYT), Int. Apdo., Postal 6-641, 06600 Mexico, D.F. Mexico.
authors.forename: Suchismita
authors.initials: S
authors.lastname: Mondal
authors.affiliation: Interdepartmental Genetics Program, Kansas State University, Manhattan, KS 66506 USA.
authors.forename: Daljit
authors.initials: D
authors.lastname: Singh
authors.affiliation: Department of Mechanical and Nuclear Engineering, Kansas State University, Manhattan, KS 66506 USA.
authors.forename: Dale
authors.initials: D
authors.lastname: Schinstock
authors.affiliation: International Maize and Wheat Improvement Center (CIMMYT), Int. Apdo., Postal 6-641, 06600 Mexico, D.F. Mexico ; International Programs of the College of Agriculture and Life Science, Cornell University, Ithaca, NY 14853 USA.
authors.forename: Jessica
authors.initials: J
authors.lastname: Rutkoski
authors.affiliation: International Maize and Wheat Improvement Center (CIMMYT), Int. Apdo., Postal 6-641, 06600 Mexico, D.F. Mexico.
authors.forename: Ivan
authors.initials: I
authors.lastname: Ortiz-Monasterio
authors.affiliation: International Maize and Wheat Improvement Center (CIMMYT), Int. Apdo., Postal 6-641, 06600 Mexico, D.F. Mexico.
authors.forename: Ravi Prakash
authors.initials: RP
authors.lastname: Singh
authors.affiliation: Department of Geography, Kansas State University, Manhattan, KS 66506 USA.
authors.forename: Douglas
authors.initials: D
authors.lastname: Goodin
authors.affiliation: Wheat Genetics Resource Center, Department of Plant Pathology and Department of Agronomy, Kansas State University, Manhattan, KS 66506 USA.
authors.forename: Jesse
authors.initials: J
authors.lastname: Poland
keywords: GNDVI; High-throughput phenotyping; Plot extraction; Remote sensing; Unmanned aerial vehicles/systems (UAV/UAS); Wheat