The Genetic Architecture of Leaf Stable Carbon Isotope Composition in Zea mays and the Effect of Transpiration Efficiency on Elemental Accumulation

With increased demand on freshwater resources for agriculture, it is imperative that more water-use efficient crops are developed. Leaf stable carbon isotope composition, δ13C, is a proxy for transpiration efficiency and a possible tool for breeders, but the underlying mechanisms effecting δ13C in C4 plants are not known. It has been suggested that differences in specific leaf area, which potentially reflects variation in internal CO2 diffusion, can impact leaf δ13C. However, at this point the relationship has not been tested in maize. Furthermore, although it is known that water movement is important for elemental uptake, it is not clear how manipulation of transpiration for increased water-use efficiency may impact nutrient accumulation. Here we characterize the underlying genetic architecture of leaf δ13C and test its relationship to specific leaf area and the ionome in four biparental populations of maize. Five significant QTL for leaf δ13C were identified, including both novel QTL as well as some that were identified previously in maize kernels. One of the QTL regions contains an Erecta-like gene, the ortholog of which has been shown to regulate transpiration efficiency and leaf δ13C in Arabidopsis. Our data does not support a relationship between δ13C and specific leaf area, and of the 19 elements analyzed, only a weak correlation between molybdenum and δ13C was detected. Together these data begin to build a genetic understanding of leaf δ13C in maize and suggest the potential to improve plant water use without significantly influencing elemental homeostasis.