Submitted to: Crop Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 10/20/2010
Publication Date: 1/27/2011
Citation: Bunce, J.A. 2011. Leaf transpiration efficiency of sweet corn varieties from three eras of breeding. Crop Science. 51:793-799.
Interpretive Summary: Changes in climate may increase the frequency of drought, making it important to increase the efficiency of water use in crop production. Modern varieties of corn have lower efficiency of water use than potentially achievable given their metabolic type. This work tested whether older varieties were more efficient. The results indicated that the efficiency of water use has not changed over the last century of breeding in sweet corn, but that significant genetic variation in the efficiency of water use exists which could be exploited to reduce the water requirements of this crop. This research will be of use to crop breeders adapting corn to dry environments and future climates.
Technical Abstract: When measured under midday field conditions, modern varieties of corn often have sub-stomatal concentrations of carbon dioxide in excess of those required to saturate photosynthesis. This results in lower leaf transpiration efficiency, the ratio of photosynthesis to transpiration, than potentially achievable for a given rate of photosynthesis. In some other crops, breeding has indirectly resulted in a large increase in stomatal conductance, which would decrease transpiration efficiency. I tested whether this occurred in sweet corn by comparing five varieties released before 1903 with four varieties released in the mid-1900’s, and four varieties released after 1990. Leaf gas exchange of each variety was measured under ambient midday field conditions in Beltsville, Maryland. Although there were significant differences among individual varieties in stomatal conductance and transpiration efficiency, no effect of era was significant. Of the four modern varieties tested, two had the highest stomatal conductance and two had the lowest conductance of any of the varieties compared, with high stomatal conductance associated with low transpiration efficiency. These four varieties were further compared in a third year, and were found to differ consistently in leaf transpiration efficiency, but not in photosynthesis. It is concluded that breeding over the last century has not increased stomatal conductance or decreased leaf transpiration efficiency in sweet corn, but that there is significant variation in transpiration efficiency among modern sweet corn varieties.