Integrating Hyperspectral Reflectance Spectroscopy into the Field Phenotyping Toolkit - A Case Study in Maize Subjected to Elevated [Ozone] in the US Mid-West

The throughput for phenotyping grain crops is seen as a major constraint to the timely release of new and improved germplasm. Remote sensing techniques at the canopy and leaf levels are currently amongst the most promising high-throughput phenotyping (HTP) approaches available. Hyperspectral reflectance spectroscopy is one HTP approach showing promise, having successfully been deployed to rapidly estimate traits related to yield (e.g., leaf N content, photosynthetic capacity and soluble sugar content) in C₃ crops. We are interested in testing the applicability of this technique in C₄ species, namely maize. Using the Free Air Concentration Enrichment (FACE) facility based in Champaign, IL to subject a genetically diverse population of maize to elevated concentrations of ozone (100 ppb), we have tested the feasibility of using leaf optical properties in the visible, near infrared and shortwave infrared regions to examine physiological processes occurring in the maize leaf subjected to oxidative stress. Fifty hybrid and inbred genotypes showing an array of physiological responses to ozone were used to build partial least squares regression (PLSR) models to estimate Rubisco kinetics, specific leaf area, sucrose and chlorophyll content. These models was then used to predict physiological responses to ozone in over 2000 plants from a panel of 26 founder and other nested associated mapping (NAM) inbred lines. Data will be presented showcasing the genetic variation for phenotypic traits relating to ozone tolerance in upper canopy leaves sampled at either pre-defined or developmentally staged time points.