Expanding the Breeder's Toolbox: The Growing Need for Field-Based Phenotyping Tools.

A significant challenge for modern plant genetics is to connect genotype with phenotype for complex traits of agronomic value. Genome-wide association studies for the near complete dissection of complex trait variation require genome-wide dense marker maps and accurate phenotyping of large segregating populations. High-throughput genotyping via whole-genome resequencing has become a reality for several plant species and the continued rapid advancements in DNA sequencing technologies will make this commonplace for many crops in the near term. In contrast, field-based, plant phenotyping methods have evolved more slowly and remained laborious and expensive over the past few decades, which has limited the dissection of difficult to measure traits, especially those related to harvestable yield and stress tolerance. In response, we have made significant progress towards the development of a tractor-based, high-throughput phenotyping (HTP) system for the simultaneous proximal remote sensing of canopy temperature, spectral reflectance, and height over the growing season and multiple times of day. Our results suggest that the HTP system can be potentially used as a tool for selecting stress tolerant lines in breeding programs and dissecting the genetic architecture of complex traits in mapping populations.