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

Abstract

In plants with C 4 photosynthesis, physiological mechanisms underlying variation in stable carbon isotope discrimination (D 13 C) are largely unknown, and genetic components influencing D 13 C have not been described. We analyzed a maize (Zea mays) introgression library derived from two elite parents to investigate whether D 13C 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 D 13C as well as plant developmental and photosynthesis-related traits. Highly heritable significant genetic variation for D 13C was detected under field and greenhouse conditions. For several introgression library lines, D 13C values consistently differed from the recurrent parent within and across the two phenotyping platforms. D 13C was significantly associated with 22 out of 164 analyzed genomic regions, indicating a complex genetic architecture of D 13C. 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 D In C 3 plants, the important steps of CO 2 uptake include the diffusion of atmospheric CO 2 through the boundary layer and the stomata. Subsequently, CO 2 is taken up by the cell and enters the chloroplast, where carboxylation by Rubisco takes place. During photosynthetic carbon fixation, the strongest fractionation of carbon isotopes occurs during the carboxylation reaction of Rubisco (Roeske and O'Leary, 1984). A theoretical model of D 13 C in C 3 photosynthesis has been described by Farquhar et al. (1982), in which D 13 C depends linearly on the ratio of intercellular to ambient partial pressure of CO 2 (p i p a 21 ), and thus provides an indication of stomatal conductance and photosynthetic capacity. Additionally, the model includes the dependency of D 13C on the fractionation of carbon isotopes during CO 2 diffusion in the air and on the enzymatic properties of the Rubisco enzyme.For rice (Oryza sativa), tomato (Solanum lycopersicum), and wheat (Triticum aestivum), it has been shown that genetic variation for D 13C is quantitative, genotype-byenvironment interaction is small, and the trait heritability is high (Condon and Richards, 1992;Rebetzke et al., 2002;Comstock et al., 2005;Impa et al., 2005). Quantitative trait

Carbon and nitrogen isotope variability in the seeds of two African millet species: Pennisetum glaucum and Eleusine coracana

“…35 The relationships between these various environmental factors and modern C 3 plant δ 13 C values have been relatively well studied (e.g., 36,37 ), and some of that work has been in Africa, 38 but there have been fewer publications focusing on environmental variation in C 4 plants. Those C 4 plants that have received attention regarding environmentally driven isotopic variation have tended to be archaeologically and economically important species, such as maize, 39,40 sorghum, 41 and, more recently, foxtail millet (Setaria italica). 17,18 The standard carbon isotope model for C 3 plants 42 posits a negative correlation between plant δ 13 C values and water availability (e.g., precipitation, relative humidity)that is, an increase in precipitation will increase stomatal conductance and in turn decrease plant δ 13 C values.…”

Bundle-sheath leakiness and intrinsic water use efficiency of a perennial C4grass are increased at high vapour pressure deficit during growth

“…Similar to the application of Δ to quantify WUE i of C 3 plants (Farquhar and Richards, 1984; Yang et al , 2016 b ), Δ was suggested as a potentially promising screening tool for breeding and improvement of C 4 crops (Henderson et al , 1998; Gresset et al , 2014; von Caemmerer et al , 2014). However, such endeavours require knowledge of the magnitude and variability of ϕ and relevant environmental drivers.…”

Management of crop water under drought: a review

“…Water saving due to higher intrinsic water-use efficiency has been popularised in breeding research with the introduction of carbon isotope discrimination (CID) as an easily measurable parameter in the mid-1980s (Farquhar and Richards 1984). CID has been assessed for various crops such as C 3 cereals (Araus et al 2002), maize (Gresset et al 2014), soybean (Gitz et al 2005), sorghum (Henderson et al 1998), faba bean (Link et al 2007) and others. CID is an indicator of conservative water use and related to earliness.…”