Accurate field canopy temperature measured in seconds

A method for cost-effective, reliable and scalable airborne thermography has been developed, resolving a number of challenges surrounding accurate high-throughput phenotyping of canopy temperature (CT) in the field, such as weather changes and their influence on more time consuming measurement methods. Utilising a manned helicopter carrying a radiometrically-calibrated thermal camera, thermal image data is captured in seconds and processed within minutes using custom-developed software; an invaluable advantage for large forward genetic studies or plant breeding programs.

The method and research results, by a collaboration between CSIRO Agriculture and Food, the Australian Plant Phenomics Facility - High Resolution Plant Phenomics Centre, CSIRO Information Management and Technology, and the ARC Centre of Excellence for Translational Photosynthesis were published recently in Frontiers in Plant Science.

Read the full study, "Methodology for high-throughput field phenotyping of canopy temperature using airborne thermography", here or the abstract below.

[caption id="attachment_1186" align="alignnone" width="850"] Airborne thermography image acquisition and processing pipeline. Total time to acquire and process images for an experiment comprising 1,000 plots of size 2 x 6 m is ca. 25 min. (A) Image acquisition with helicopter. The images are recorded on a laptop and the passenger, left, provides real time assessment of the images and feedback to the pilot. This step takes < 10 s for an experiment comprising 1,000 plots of size 2 x 6 m. (B) Screenshot of custom-developed software called ChopIt. ChopIt is used for plot segmentation and extraction of CT from each individual plot for statistical analysis. This step takes ca. 20 min for an experiment comprising 1,000 plots of size 2 x 6 m.[/caption]

[caption id="attachment_1183" align="alignnone" width="850"] Airborne thermography image acquisition system comprising a helicopter cargo pod with thermal camera and acquisition kit mounted on the skid of a Robinson R44 Ravel helicopter. Photo insert shows the inside of the helicopter cargo pod with arrow denoting FLR® SC645 thermal camera: ±2°C or ±2% of reading; < 0.05°C pixel sensitivity; 640x480 pixels; 0.7 kg without lens.[/caption]

Abstract

Lower canopy temperature (CT), resulting from increased stomatal conductance, has been associated with increased yield in wheat. Historically, CT has been measured with hand-held infrared thermometers. Using the hand-held CT method on large field trials is problematic, mostly because measurements are confounded by temporal weather changes during the time required to measure all plots. The hand-held CT method is laborious and yet the resulting heritability low, thereby reducing confidence in selection in large scale breeding endeavors. We have developed a reliable and scalable crop phenotyping method for assessing CT in large field experiments. The method involves airborne thermography from a manned helicopter using a radiometrically-calibrated thermal camera. Thermal image data is acquired from large experiments in the order of seconds, thereby enabling simultaneous measurement of CT on potentially 1000s of plots. Effects of temporal weather variation when phenotyping large experiments using hand-held infrared thermometers are therefore reduced. The method is designed for cost-effective and large-scale use by the non-technical user and includes custom-developed software for data processing to obtain CT data on a single-plot basis for analysis. Broad-sense heritability was routinely >0.50, and as high as 0.79, for airborne thermography CT measured near anthesis on a wheat experiment comprising 768 plots of size 2 × 6 m. Image analysis based on the frequency distribution of temperature pixels to remove the possible influence of background soil did not improve broad-sense heritability. Total image acquisition and processing time was ca. 25 min and required only one person (excluding the helicopter pilot). The results indicate the potential to phenotype CT on large populations in genetics studies or for selection within a plant breeding program.

Citation:  Deery DM, Rebetzke GJ, Jimenez-Berni JA, James RA, Condon AG, Bovill WD, Hutchinson P, Scarrow J, Davy R and Furbank RT (2016) Methodology for High-Throughput Field Phenotyping of Canopy Temperature Using Airborne Thermography. Front. Plant Sci. 7:1808. doi: 10.3389/fpls.2016.01808

10 January 2017