Methodology for High-Throughput Field Phenotyping of Canopy Temperature Using Airborne Thermography

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.

High‐Throughput Approaches for Phenotyping Alfalfa Germplasm under Abiotic Stress in the Field

“…Once the infrastructure for RS approaches is in place, their successful deployment for phenotyping forage species for biomass yield and persistence as part of trait-development and breeding programs can be used to reliably identify differences among genotypes. Additional benefits of these and other sensor-based methods include relatively fast data acquisition and data processing, among others, as described by Deery et al (2016). Further benefits will be obtained as these strategies are deployed to evaluate progenies resulting from multiple cycles of selection, intermating, and evaluation aimed at increasing yield and persistence under low-input conditions.…”

UAV and Ground Image-Based Phenotyping: A Proof of Concept with Durum Wheat

“…Further benefits of the simultaneous characterization of many plots are found by minimizing the effect of the changing environmental conditions associated with time-consuming ground measurements. This is evident especially when measuring the canopy temperature [12], which greatly varies throughout the day. In recent years, a considerable bulk of the literature has clearly demonstrated the potential of unmanned airborne platforms for large-scale crop monitoring, mainly due to the high spatial and spectral resolution of the sensors [13,14].…”

Modelling of genotype by environment interaction and prediction of complex traits across multiple environments as a synthesis of crop growth modelling, genetics and statistics

“…Phenotyping techniques can be applied in facilities under controlled conditions, generally not transportable (platforms, Junker et al 2015;Neumann et al 2015) or can be based on mobile devices for field conditions (e.g. drones, helicopters, mobile devices, Chapman et al 2014;Deery et al 2014Deery et al , 2016. In general, there is no clear strategy about which types of facilities can best be used in which breeding situations.…”

“…Examples for the use of platforms/controlled conditions to characterize basic traits are wheat early vigour measured in the greenhouse (Duan et al, 2016), the root angle in maize and sorghum measured in greenhouse pots as a trait related to water uptake (Singh et al 2010), or the sensitivity to photoperiod, vernalization and earliness per se in wheat measured in controlled conditions for photoperiod and temperature (Zheng et al 2013;Sukumaran et al 2016). Examples for intermediate traits in field conditions are airborne measurements for wheat NDVI and canopy temperature (Deery et al 2016;Rutkoski et al 2016).…”