|ELLSWORTH, PATRICK - Washington State University|
|BAXTER, IVAN - Danforth Plant Science Center|
|COUSINS, ASAPH - Central Washington University|
Submitted to: Plant Journal
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/2/2020
Publication Date: 6/18/2020
Citation: Ellsworth, P.Z., Feldman, M.J., Baxter, I.R., Cousins, A.B. 2020. A genetic link between leaf carbon istope composition and whole-plant water use efficiency in the C4 grass setaria. Plant Journal. https://doi.org/10.1111/tpj.14696.
Interpretive Summary: Improving agricultural productivity while reducing the volume of fresh water needed for irrigation has been a long-term goal of many plant breeding programs. Water use efficiency (WUE), the ratio of plant biomass produced relative to the volume of water used, is a complex characteristic that is influenced by many different factors. Identifying regions of the genome that influence this trait is a challenge, primarily due to difficulty measuring this characteristic across large numbers of individuals within breeding populations. The recent development of robotic phenotyping instruments and carbon isotope measurement using mass spectrometry enable scientists to measure plant components that may directly relate to WUE more accurately and with less effort. This study utilized these two high-throughput methods to quantify WUE in a biparental recombinant inbred line population of a model, warm-season grass species (Setaria sp.) within a well-watered and water-limited growth environment. This study identified overlapping genomic regions associated with the volume of water transpired, plant biomass produced and carbon isotope ratio suggesting that each of these methods are suitable for monitoring WUE in large breeding populations.
Technical Abstract: Genetic selection for whole plant water use efficiency (yield per transpiration; WUEplant) in any crop-breeding program requires high throughput phenotyping of component traits of WUEplant such as transpiration efficiency (TEi; CO2 assimilation rate per stomatal conductance). Leaf carbon stable isotope composition (d13Cleaf) has been suggested as a potential proxy for WUEplant because both parameters are influenced by TEi. However, a genetic link between d13Cleaf and WUEplant in a C4 species is still not well understood. Therefore, a high throughput phenotyping facility was used to measure WUEplant in a recombinant inbred line (RIL) population of the C4 grasses Setaria viridis and S. italica to determine the genetic relationship between d13Cleaf, WUEplant, and TEi under well-watered and water-limited growth conditions. Three quantitative trait loci (QTL) for d13Cleaf were found to co-localize with transpiration, biomass accumulation, and WUEplant. WUEplant calculated for each of the three d13Cleaf allele classes was negatively correlated with d13Cleaf as would be predicted when TEi is driving WUEplant. These results demonstrate that d13Cleaf is genetically linked to WUEplant through TEi and can be used as a high throughput proxy to screen for WUEplant in these species.