Deery David M, Rebetzke Greg J, Jimenez-Berni Jose A, Bovill William D, James Richard A, Condon Anthony G, Furbank Robert T, Chapman Scott C, Fischer Ralph A
CSIRO Agriculture and Food, Canberra, ACT, Australia.
ARC Centre of Excellence for Translational Photosynthesis, Australian National University, Canberra, ACT, Australia.
Front Plant Sci. 2019 Jul 9;10:875. doi: 10.3389/fpls.2019.00875. eCollection 2019.
Infrared canopy temperature (CT) is a well-established surrogate measure of stomatal conductance. There is ample evidence showing that genotypic variation in stomatal conductance is associated with grain yield in wheat. Our goal was to determine when CT repeatability is greatest (throughout the season and within the day) to guide CT deployment for research and wheat breeding. CT was measured continuously with ArduCrop wireless infrared thermometers from post-tillering to physiological maturity, and with airborne thermography on cloudless days from manned helicopter at multiple times before and after flowering. Our experiments in wheat, across two years contrasting for water availability, showed that repeatability for CT was greatest later in the season, during grain-filling, and usually in the afternoon. This was supported by the observation that repeatability for ArduCrop, and more so for airborne CT, was significantly associated ( < 0.0001) with calculated clear-sky solar radiation and to a lesser degree, vapor pressure deficit. Adding vapor pressure deficit to a model comprising either clear-sky solar radiation or its determinants, day-of-year and hour-of-day, made little to no improvement to the coefficient of determination. Phenotypic correlations for airborne CT afternoon sampling events were consistently high between events in the same year, more so for the year when soil water was plentiful ( = 0.7 to 0.9) than the year where soil water was limiting ( = 0.4 to 0.9). Phenotypic correlations for afternoon airborne CT were moderate between years contrasting in soil water availability ( = 0.1 to 0.5) and notably greater on two separate days following irrigation or rain in the drier year, ranging from = 0.39 to 0.53 ( < 0.0001) for the midday events. For ArduCrop CT the pattern of phenotypic correlations, within a given year, was similar for both years: phenotypic correlations were higher during the grain-filling months of October and November and for hours-of-day from 11 onwards. The lowest correlations comprised events from hours-of-day 8 and 9 across all months. The capacity for the airborne method to instantaneously sample CT on hundreds of plots is more suited to large field experiments than the static ArduCrop sensors which measure CT continuously on a single experimental plot at any given time. Our findings provide promising support for the reliable deployment of CT phenotyping for research and wheat breeding, whereby the high repeatability and high phenotypic correlations between afternoon sampling events during grain-filling could enable reliable screening of germplasm from only one or two sampling events.
红外冠层温度（CT）是气孔导度一种公认的替代指标。有充分证据表明，气孔导度的基因型变异与小麦籽粒产量相关。我们的目标是确定CT重复性何时最高（整个生长季以及一天之中），以指导CT在研究和小麦育种中的应用。从分蘖后期到生理成熟期，使用ArduCrop无线红外温度计连续测量CT，并在开花前后多次通过载人直升机在无云天气下进行机载热成像测量。我们在小麦上进行了为期两年的试验，这两年的水分供应情况不同，结果表明，CT的重复性在生长季后期、灌浆期以及通常在下午时最高。这一结果得到以下观察结果的支持：ArduCrop的重复性，尤其是机载CT的重复性，与计算得出的晴空太阳辐射显著相关（<0.0001），与水汽压亏缺的相关性较小。在包含晴空太阳辐射或其决定因素（一年中的日期和一天中的时间）的模型中加入水汽压亏缺，对决定系数几乎没有改善。同年同一天下午机载CT采样事件之间的表型相关性始终很高，土壤水分充足年份（=0.7至0.9）的相关性高于土壤水分受限年份（=0.4至0.9）。在土壤水分供应情况不同的年份之间，下午机载CT的表型相关性适中（=0.1至0.5），在较干旱年份灌溉或降雨后的两个不同日期，相关性显著更高，中午事件的相关性范围为=0.39至0.53（<0.0001）。对于ArduCrop CT，在给定年份内，两年的表型相关性模式相似：在10月和11月的灌浆月份以及11点及以后的一天中的时间，表型相关性较高。所有月份中，相关性最低的是8点和9点的事件。与在任何给定时间在单个试验小区上连续测量CT的静态ArduCrop传感器相比，机载方法能够在数百个小区上即时采样CT的能力更适合大型田间试验。我们的研究结果为CT表型分析在研究和小麦育种中的可靠应用提供了有力支持，即灌浆期下午采样事件之间的高重复性和高表型相关性能够仅通过一两个采样事件就可靠地筛选种质。
