Leveraging the Diversity and Genomic Resources of Maize to Investigate Photosynthesis and Transpiration

The vast genetic resources available in maize make it an ideal system for studying complex traits. However, the diversity of maize has been underutilized as a tool for studying photosynthesis. One important aspect of leaf photosynthesis is the relationship between CO₂ uptake and transpirational water loss. Even a modest reduction in transpiration, while maintaining rates of photosynthesis, would constitute substantial water savings for maize cultivated under both irrigated and unirrigated conditions. These water savings are even more critical under water stress conditions, which are predicted to be more frequent and severe in the future (Cook et al., 2015 Science Advances: e1400082). Our research focuses on identifying the genetic control of leaf traits that alter photosynthesis and transpiration. The ratio of stable carbon isotopes (¹³C and ¹²C, ratio abbreviated δ¹³C) in leaf tissue is affected by the enzymes utilized by the photosynthetic pathway and by the plants water-use efficiency. We have identified significant variation in existing mapping populations for leaf δ¹³C that is robust across environments, making it an excellent trait for genetic analysis and an entry point for subsequent detailed physiological characterization. Quantitative genetic approaches are being used to map variation in leaf δ¹³C and link it to leaf morphology. These findings will be incorporated into elite germplasm and tested under agronomically relevant conditions.