Summary
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 (δ13Cleaf) has been suggested as a potential proxy for WUEplant because both parameters are influenced by TEi. However, a genetic link between δ13Cleaf 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 δ13Cleaf, WUEplant, and TEi under well-watered and water-limited growth conditions.
Three quantitative trait loci (QTL) for δ13Cleaf were found to co-localize with transpiration, biomass accumulation, and WUEplant. WUEplant calculated for each of the three δ13Cleaf allele classes was negatively correlated with δ13Cleaf as would be predicted when TEi is driving WUEplant.
These results demonstrate that δ13Cleaf is genetically linked to WUEplant through TEi and can be used as a high throughput proxy to screen for WUEplant in these C4 species.
