A genetic link between leaf carbon isotope composition and whole‐plant water use efficiency in the C4 grass Setaria

• Published in: The Plant journal : for cell and molecular biology Vol. 102; no. 6; pp. 1234 - 1248
• Main Authors: Ellsworth, Patrick Z., Feldman, Max J., Baxter, Ivan, Cousins, Asaph B.
• Format: Journal Article
• Language: English
• Published: Oxford Blackwell Publishing Ltd 01.06.2020; Society for Experimental Biology
• Subjects: BASIC BIOLOGICAL SCIENCES; C4 photosynthesis; Carbon dioxide; Carbon isotopes; Conductance; drought; Efficiency; Gas exchange; Gene mapping; genetic architecture; Genetic relationship; Grasses; Growth conditions; Inbreeding; Isotope composition; Isotopes; leaf carbon isotopes; Leaves; Phenotyping; Plant breeding; Quantitative trait loci; recombinant inbred lines; Resistance; Setaria; Stable isotopes; Stomata; Stomatal conductance; Transpiration; Water use; Water use efficiency
• ISSN: 0960-7412; 1365-313X
• DOI: 10.1111/tpj.14696

Summary Genetic selection for whole‐plant water use efficiency (yield per transpiration; WUEplant) in any crop‐breeding programme requires high‐throughput phenotyping of component traits of WUEplant such as intrinsic water use efficiency (WUEi; CO2 assimilation rate per stomatal conductance). Measuring WUEi by gas exchange measurements is laborious and time consuming and may not reflect an integrated WUEi over the life of the leaf. Alternatively, leaf carbon stable isotope composition (δ13Cleaf) has been suggested as a potential time‐integrated proxy for WUEi that may provide a tool to screen for WUEplant. However, a genetic link between δ13Cleaf and WUEplant in a C4 species has not been well established. Therefore, to determine if there is a genetic relationship in a C4 plant between δ13Cleaf and WUEplant under well watered and water‐limited growth conditions, a high‐throughput phenotyping facility was used to measure WUEplant in a recombinant inbred line (RIL) population created between the C4 grasses Setaria viridis and S. italica. Three quantitative trait loci (QTL) for δ13Cleaf were found and co‐localized with transpiration, biomass accumulation, and WUEplant. Additionally, WUEplant for each of the δ13Cleaf QTL allele classes was negatively correlated with δ13Cleaf, as would be predicted when WUEi influences WUEplant. These results demonstrate that δ13Cleaf is genetically linked to WUEplant, likely to be through their relationship with WUEi, and can be used as a high‐throughput proxy to screen for WUEplant in these C4 species. Significance Statement Improving whole‐plant water use efficiency (WUEplant) can reduce agricultural demand for freshwater but it can be difficult to measure. Therefore, leaf carbon isotopic composition (δ13Cleaf) has been proposed as a proxy for WUEplant in C4 plant species. We found that the δ13Cleaf shares a similar genetic architecture with WUEplant and its component traits (biomass accumulation and transpiration) in the C4 grass Setaria, suggesting that δ13Cleaf can be an effective screening tool for WUEplant.