Stable Carbon Isotope Discrimination Is under Genetic Control in the C4 Species Maize with Several Genomic Regions Influencing Trait Expression

In plants with C-4 photosynthesis, physiological mechanisms underlying variation in stable carbon isotope discrimination (Delta C-13) are largely unknown, and genetic components influencing Delta C-13 have not been described. We analyzed a maize (Zea mays) introgression library derived from two elite parents to investigate whether Delta C-13 is under genetic control in this C-4 species. High-density genotyping with the Illumina MaizeSNP50 Bead Chip was used for a detailed structural characterization of 89 introgression lines. Phenotypic analyses were conducted in the field and in the greenhouse for kernel Delta C-13 as well as plant developmental and photosynthesis-related traits. Highly heritable significant genetic variation for Delta C-13 was detected under field and greenhouse conditions. For several introgression library lines, Delta C-13 values consistently differed from the recurrent parent within and across the two phenotyping platforms. Delta C-13 was significantly associated with 22 out of 164 analyzed genomic regions, indicating a complex genetic architecture of Delta C-13. The five genomic regions with the largest effects were located on chromosomes 1, 2, 6, 7, and 9 and explained 55% of the phenotypic variation for Delta C-13. Plant development stage had no effect on Delta C-13 expression, as phenotypic as well as genotypic correlations between Delta C-13, flowering time, and plant height were not significant. To our knowledge, this is the first study demonstrating Delta C-13 to be under polygenic control in the C-4 species maize.