Genotypic diversity in the responses of yield, yield components, grain quality and progression of developmental processes to elevated ozone of diverse inbred and hybrid maize

Ozone related stress has been shown to cause significant yield loss in many major crops. However, little experimental data is available on maize responses to ozone. And, in general, the extent of genetic diversity in response to ozone is poorly understood. Free-Air Concentration Enrichment (FACE) experiments allow crops to be grown at elevated ozone concentrations in an open-air, farm field setting. This makes the results of the studies more relevant to production agriculture. FACE experiments provide large areas for plant growth that allow more genotypes to be tested throughout the entire crop lifecycle than is possible in controlled environment facilities. This project leveraged these capabilities of the SoyFACE facility, located in the major maize growing region of the Midwest U.S., to evaluate genetic variation in ozone effects on diverse populations of inbred and hybrid maize over multiple growing seasons. Both inbreds and hybrids demonstrated substantial genetic variation in their sensitivity to ozone. The average grain yield loss was 11% in inbred genotypes and 16% in hybrid genotypes. This provides key experimental evidence to support previous estimates of predicted grain yield loss due to concurrent ozone concentration from regression analysis of variation in ozone concentrations and crop yields over space and time. Overall, the grain yield component driving yield loss was kernel number for inbred maize genotypes. In the hybrid maize genotypes, grain yield loss was significantly associated with ozone effects on both grain yield components, kernel number and individual kernel mass, and the progression of canopy senescence. Grain yield loss from ozone sensitivity could not be predicted from grain yield of ambient grown plants. These findings suggest that there is heritable genetic variation in response to ozone that could be basis for selection to improve maize grain yields. Although additional work will be needed to test for the relevant alleles in elite germplasm that is grown for production. Development of more ozone tolerant genotypes would have significant global agronomic impact given the importance of maize as the most important crop in terms of production, with diverse uses in feed, food, and fuel