Abstract
The study of phenotypes that reveal mechanisms of adaptation to drought and heat stress is crucial for the development of climate resilient crops in the face of climate uncertainty. The leaf metabolome effectively summarizes stress-driven perturbations of the plant physiological status and represents an intermediate phenotype that bridges the plant genome and phenome. The objective of this study was to analyze the effect of water deficit and heat stress on the leaf metabolome of 22 genetically diverse accessions of upland cotton grown in the Arizona low desert over two consecutive years. Results revealed that membrane lipid remodeling was the main leaf mechanism of adaptation to drought. The magnitude of metabolic adaptations to drought, which had an impact on fiber traits, was found to be quantitatively and qualitatively associated with different stress severity levels during the two years of the field trial. Leaf-level hyperspectral reflectance data were also used to predict the leaf metabolite profiles of the cotton accessions. Multivariate statistical models using hyperspectral data accurately estimated (R2 > 0.7 in ∼34% of the metabolites) and predicted (Q2 > 0.5 in 15–25% of the metabolites) many leaf metabolites. Predicted values of metabolites could efficiently discriminate stressed and non-stressed samples and reveal which regions of the reflectance spectrum were the most informative for predictions. Combined together, these findings suggest that hyperspectral sensors can be used for the rapid, non-destructive estimation of leaf metabolites, which can summarize the plant physiological status.
Highlights
Drought and heat are two major abiotic stresses that often occur in the field simultaneously and whose effects negatively impact crop growth and productivity (Mittler, 2006; Suzuki et al, 2014)
When cotton is grown in semi-arid environments, well above the thermal optimum of 30/22◦C day/night temperature (Burke and Wanjura, 2010), water availability is associated with heat stress avoidance through transpiration-driven leaf cooling that, on very hot days, can reach 10◦C relative to ambient atmospheric temperatures (Burke and Upchurch, 1989; Carmo-Silva et al, 2012)
A major goal of this work was to analyze the leaf metabolic responses to heat stress and water limitations in a set of genetically diverse cotton accessions grown in the Arizona low desert over two consecutive years
Summary
Drought and heat are two major abiotic stresses that often occur in the field simultaneously and whose effects negatively impact crop growth and productivity (Mittler, 2006; Suzuki et al, 2014). When cotton is grown in semi-arid environments, well above the thermal optimum of 30/22◦C day/night temperature (Burke and Wanjura, 2010), water availability is associated with heat stress avoidance through transpiration-driven leaf cooling that, on very hot days, can reach 10◦C relative to ambient atmospheric temperatures (Burke and Upchurch, 1989; Carmo-Silva et al, 2012) In this context, the ongoing drought in the Colorado River basin, the main source of irrigation water for Arizona growers, and the projected increase in temperature due to global climate change are estimated to cause ∼40 and ∼50% reduction in cotton yield by mid- and late-century, respectively (Ayankojo et al, 2020; Thorp et al, 2020). For these reasons, is necessary the development of new cotton accessions more adapted to heat and drought stress
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