Uncovering hidden genetic variation in photosynthesis of field-grown maize under ozone pollution

Authors: CHOQUETTE, N - University Of Illinois; OGUT, F - University Of Florida; WERTIN, T - University Of Illinois; MONTES, C - University Of Illinois; SORGINI, C - University Of Illinois; MORSE, A - University Of Florida; BROWN, P - University Of Illinois; LEAKEY, A D B - University Of Illinois; MCINTYRE, L - University Of Florida; Ainsworth, Elizabeth - Lisa

Submitted to: Global Change Biology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 8/7/2019
Publication Date: 10/1/2019
Citation: Choquette, N.E., Ogut, F., Wertin, T.M., Montes, C.M., Sorgini, C.A., Morse, A.M., Brown, P.J., Leakey, A., McIntyre, L.M., Ainsworth, E.A. 2019. Uncovering hidden genetic variation in photosynthesis of field-grown maize under ozone pollution. Global Change Biology. 25(12):4327-4338. https://doi.org/10.1111/gcb.14794.
DOI: https://doi.org/10.1111/gcb.14794

Interpretive Summary: Ozone is a damaging air pollutant to crops, currently costing Midwest U.S. maize producers up to 10% of potential yields. However, there has been little effort to adapt germplasm for ozone tolerance. In this study, ten diverse inbred maize lines parents were crossed with one another to create 45 F1 hybrids, which were tested for ozone response in the field. Ozone stress altered the heritability of photosynthesis and hybrids created from Hp301 and NC338 were particularly sensitive to ozone. This implies that past selection of maize under current ambient ozone will not have selected against alleles that confer sensitivity to ozone pollution, and further selection under elevated ozone concentrations might purge deleterious alleles. More broadly, this work demonstrates the capability of free air ozone enrichment technology to be used for field experimentation on diverse populations of major commodity crops to address needs for adaptation to pollution and climatic change that cannot be easily accomplished by other existing approaches.

Technical Abstract: Ozone is the most damaging air pollutant to crops, currently reducing Midwest U.S. maize production by up to 10%, yet there has been very little effort to adapt germplasm for ozone tolerance. Ozone enters plants through stomata, reacts to form reactive oxygen species in the apoplast, and ultimately decreases photosynthetic C gain. In this study, ten diverse inbred parents were crossed in a half-diallel design to create 45 F1 hybrids, which were tested for ozone response in the field using Free Air Concentration Enrichment (FACE). Ozone stress increased the heritability of photosynthetic traits and altered genetic correlations among traits. Hybrids from parents Hp301 and NC338 showed greater sensitivity to ozone stress, and disrupted relationships among photosynthetic traits. The physiological responses underlying sensitivity to ozone differed in hybrids from the two parents, suggesting multiple mechanisms of response to oxidative stress. FACE technology was essential to this evaluation because genetic variation in photosynthesis under elevated ozone was not predictable based on performance at ambient ozone. These findings suggest that selection under elevated ozone is needed to identify deleterious alleles in the world’s largest commodity crop.