1a. Objectives (from AD-416)
This research will investigate the response of random inbred lines of soybean to elevated ozone concentrations in the field at the SoyFACE experiment. We will use existing tools from high throughput genomics, metabolomics, comparative and quantitative genetics, and bioinformatics to elucidate the mechanisms of soybean yield response to elevated ozone.
1b. Approach (from AD-416)
This project will use physiological and biochemical analysis, comparative and quantitative genetics, and bioinformatics to study the mechanisms of soybean yield response to elevated ozone.
3. Progress Report
We identified two soybean genotypes, Dwight and Pana, with different yield responses to elevated ozone. Hybrid F1 seed was produced from these cultivars in 2008. Development of this experimental population prior to 2010 involved advancement of lines from the F2 to the F5 generation through single seed descent. The F5 seed was planted in the field under ambient conditions in 2010 in order to generate sufficient F6 RIL seed for the 2011 ozone field experiment. To ensure ozone response will not be confounded by time to maturity, RILs that showed transgressive segregation for maturity under ambient field conditions in 2010 were identified and excluded from the 2011 experiment. In 2010, the parent lines were also grown under 9 different ozone concentrations at the SoyFACE facility in Urbana, Illinois, in order to characterize their dose-response and to identify the optimal elevated ozone concentration for the 2011 and 2012 experiments. Photosynthesis, leaf area development, antioxidant capacity, and yield of the parent lines were also assessed. An experiment involving 10 soybean cultivars was performed to evaluate agronomic and seed composition changes caused by exposure to elevated ozone concentrations. The 10 cultivars selected have all contributed significantly to North American soybean breeding efforts. Field observations were made to evaluate appropriate response variables and estimate their correlation with yield loss due to elevated ozone. Evaluated responses included foliar damage, leaf chlorophyll content, photosynthetic rates, plant height, stem diameter, leaf size, time to maturity, seed weight, seed oil/protein content, and yield. Highly significant relationships were observed between all of these responses and ozone concentration, while the strongest correlations with yield loss due to ozone were with physiological responses such as plant height, leaf size, and foliar damage. Although little effect on seed oil and protein content was observed, seed from plants grown in elevated ozone showed an altered fatty acid profile, resulting in seed with higher levels of undesirable polyunsaturated fatty acids. Preliminary results from this work were presented in 5 oral presentations at the 2011 Soybean Breeders Workshop, the Gordon Conference on CO2 assimilation, the Society for Experimental Biology annual meeting, the University of Wisconsin and the University of Illinois. We have also started a collaboration with an ARS researcher in St. Louis, MO, to evaluate the ion content on the soybean seed exposed to elevated ozone.