Advancements in phenotyping techniques capable of rapidly and nondestructively detecting impacts of drought on crops are necessary to meet the 21st-century challenge of food security. Here, we describe the use of hyperspectral reflectance to predict variation in physiological and anatomical leaf traits related with water status under varying water availability in six maize (Zea mays) hybrids that differ in yield stability under drought. We also assessed relationships among traits and collections of traits with yield stability. Measurements were collected in both greenhouse and field environments, with plants exposed to different levels of water stress or to natural water availability, respectively. Leaf spectral measurements were paired with a number of physiological and anatomical reference measurements, and predictive spectral models were constructed using a partial leastsquares regression approach. All traits were relatively well predicted by spectroscopic models, with external validation (i.e. by applying partial least-squares regression coefficients on a dataset distinct from the one used for calibration) goodness-of-fit (R2) ranging from 0.37 to 0.89 and normalized error ranging from 12% to 21%. Correlations between reference and predicted data were statistically similar for both greenhouse and field data. Our findings highlight the capability of vegetation spectroscopy to rapidly and nondestructively identify a number of foliar functional traits affected by drought that can be used as indicators of plant water status. Although we did not detect trait coordination with yield stability in the hybrids used in this study, expanding the range of functional traits estimated by hyperspectral data can help improve trait-based breeding approaches.
One of the more influential, yet unpredictable, factors expected to change in future environments over the next 50 years will be the intensity and frequency of precipitation events (Intergovernmental Panel on Climate Change, 2014). These changes will likely have a dramatic effect on plant metabolism, growth, and production (Pryor et al., 2013; Miao et al., 2017). Over a comparable time period, global food demand is predicted to double, requiring intensification of agricultural production systems (Tilman et al., 2011). The rapid development and adoption of climate-resilient crop genotypes capable ofmaintaining comparable yield production under favorable and stress conditions (i.e. with high yield stability) is important to overcome this 21stcentury challenge (Mickelbart et al., 2015). Advancements in phenotyping techniques capable of rapidly assessing the effects of drought on plant functional responses from a wide genetic range is necessary to understand plant traits required to maintain yield stability under predicted future environmental conditions (Araus et al., 2012; Cotrozzi et al., 2017; Miao et al., 2017).
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