|VANLOOCKE, ANDY - Former ARS Employee|
|ZHU, XIN-GUANG - Chinese Academy Of Sciences|
Submitted to: Frontiers in Plant Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/27/2017
Publication Date: 4/18/2017
Citation: Slattery, R.A., VanLoocke, A., Bernacchi, C.J., Zhu, X., Ort, D.R. 2017. Photosynthesis, light use efficiency, and yield of reduced-chlorophyll soybean mutants in field conditions. Frontiers in Plant Physiology. doi.org/10.3389/fpls.2017.00549.
Interpretive Summary: Soybean is the world’s third most economically important commodity crop. At agricultural planting densities, soybean develops a dense canopy with a leaf area index often greater than six. This creates a situation in which the majority of leaves are experiencing light levels below the light compensation point during most daylight hours and makes it an ideal candidate crop for testing the effects of reduced chl content on ec. In addition, a previous field experiment reported greater Acan in two chl b-deficient soybean mutants compared to the nearly isogenic “Clark” wild type throughout the growing season. However, comprehensive studies of reduced chl effects on soybean at both the leaf and canopy scale have not yet been conducted in the same experiment. Therefore, light green soybean mutants were grown in the field over two growing seasons, one of which implemented a row spacing treatment, to test the hypothesis that reducing chl content will increase leaf and canopy photosynthesis and photosynthetic efficiency, and ultimately lead to greater yields.
Technical Abstract: Reducing chlorophyll (chl) content may improve the conversion efficiency of absorbed radiation into biomass (ec) and therefore yield in dense monoculture crops by improving light penetration and distribution within the canopy. Modeling suggests that reducing chl content may also reduce leaf temperature, increase water use efficiency (WUE), and allow for the diversion of nitrogen to rate-limiting photosynthetic enzymes. The effects of reduced chl on leaf and canopy processes were studied in chl b deficient soybean mutants during the 2012 and 2013 growing seasons. Chl deficiency showed the greatest benefit to leaf photosynthetic light use efficiency early in the growing season when mutant chl content was lowest at ~65 % of the WT. ec was not significantly different between genotypes, and seed yield was similar or greater in WT. The mutant canopies absorbed less energy over the growing season, and the specific mutation causing chl deficiency was associated with lower WUE and thus greater susceptibility of the mutants to the drought conditions that occurred both years of the field study. Therefore, a more fine-tuned approach to maintaining optimal chl content throughout the growing season while avoiding detrimental pleiotropic effects of the mutations will be needed to see the anticipated improvement of canopy ec and yield of the light green phenotype.