Submitted to: International Journal of Agronomy
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 12/10/2014
Publication Date: 1/9/2015
Citation: Bruns, H.A. 2015. Ear leaf photosynthesis and related parameters of transgenic and non-GMO maize hybrids. International Journal of Agronomy. 2015:1-5. doi:10.1155/2015/731351.
Interpretive Summary: Hybrid corn has been altered over the past decade through transgenics, to have resistance to some of the more serious corn insect pests, tolerance to specific herbicides, and now a combination of both traits. It was not known if these transgenic changes had affected some of the basic physiological processes of the plant that are involved in creating yield. Photosynthesis, the biological process of combining CO2 from the air with water, in the leaf during the day was measured along with stomatal conductance, transpiration, water use efficiency, and internal CO2 concentration on both transgenic (8 hybrids) and conventional (2 hybrids). The experiment was conducted on two sites, a fine sandy loam soil and a heavy clay soil, by a scientist at the USDA, ARS, Crop Production Systems Research Unit, Stoneville, MS in 2011 and 2012. Both fields were furrow irrigated. Measurements were taken at 50% silking and again at early kernel filling. No consistent differences in photosynthesis or other related parameters were noted that would have given any particular hybrid or group of hybrids (transgenic vs. conventional) an advantage in eventual yield due to improved rates of photosynthesis or the other parameters that were measured. This information will be of particular interest to other scientists, especially those in hybrid seed corn development.
Technical Abstract: Hybrid maize (Zea mays L.) has undergone transformation by using transgenic technology to include d-endotoxins for insect control and tolerance for the herbicides glyphosate and glufosinate . Maize hybrids are being grown with multiple transgenic traits into their genotype (stacked-gene). Limited information is available on how the presence of these traits, minus the presence of the controlled pests or use of the specific herbicides affect A and related physiological parameters. A two year, two location (a Bosket fine sandy loam Fine-loamy, mixed, active, thermic Mollic Hapludalfs and Tunica clay clayey over loamy, smectitic, nonacid, thermic Vertic Haplaquept), irrigated experiment comparing four stacked-gene, four glyphosate tolerant, and two non-GMO maize hybrids for ear leaf A, gs, Em, WUE, and Ci, was completed at Stoneville, MS in 2012. Data were collected at Growth Stages R1 (anthesis) and R2 (early kernel filling) using a LiCor LI-6400 XT set at 355 µmol mol-1 CO2 with a flow rate of 500 µmol s-1 and a 6400-02 light source set at 87.5% full sunlight. Measurements were made between 08:30 h and 11:30 h CST, within 48 h of an irrigation of 25 ha mm, and >33.0% cloud cover. Transgenic traits incorporated into the maize hybrid genotypes to impart insect resistance and herbicide tolerance did not influence the physiological traits of A, gs, Em, WUE, of Ci during the critical growth stages of anthesis (R1), or early kernel filling (R2).