The genetic architecture of leaf stable carbon isotope composition in Zea mays and the effect of transpiration efficiency on leaf 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, delta C-13, is a proxy for transpiration efficiency and a possible tool for breeders, but the underlying mechanisms effecting delta C-13 in C-4 plants are not known. It has been suggested that differences in specific leaf area (SLA), which potentially reflects variation in internal CO2 diffusion, can impact leaf delta C-13. 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 genetic architecture of leaf delta C-13 and test its relationship to SLA and the ionome in five populations of maize. Five significant QTL for leaf delta C-13 were identified, including 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 delta C-13 in Arabidopsis. QTL for delta C-13 were located in the same general chromosome region, but slightly shifted, when comparing data from two different years. Our data does not support a relationship between delta C-13 and SLA, and of the 19 elements analyzed, only a weak correlation between molybdenum and delta C-13 was detected. Together these data add to the genetic understanding of leaf delta C-13 in maize and suggest that improvements to plant water use may be possible without significantly influencing elemental homeostasis.