Genotypic Diversity in Yield and Grain Quality Responses to Elevated Ozone of Diverse Inbred and Hybrid Maize

Oxidative stress from exposure to tropospheric ozone (O₃) currently causes significant yield losses in the world’s major crops. This represents economic losses of ~$14 to $26 billion and is predicted to increase as pollution emissions increase in key growing regions this century. However, little is known about the genetic and genomic basis for yield loss to oxidative stress in any crop, but especially C4 crops like maize. The yield and grain quality of maize were compared under ambient (~40 ppb) and elevated O₃ concentrations (100 ppb) over two growing seasons at the Free Air Concentration Enrichment (FACE) site in Champaign, IL. In 2014, 52 inbred lines representing the extremes of O₃ sensitivity were tested in addition to 26 hybrids. In 2015, 10 inbred lines were re-tested in addition to 8 hybrid lines. Ear mass was, on average, significantly lower in inbred (-7%) and hybrid (-9%) lines. But, some lines were sensitive to yield loss (up to -76% in inbreds and -26% in hybrids) while others were highly tolerant of growth at elevated O₃. Yield loss was primarily driven by decreased kernel number on inbreds versus decreased individual kernel mass in hybrids. Yield loss was also associated with increased kernel protein content under elevated O₃. Current analyses are evaluating kernel growth rate and grain-filling period to assess whether reduced photoassimilate supply or a shorter grain filling period causes yield loss.