Assessing diversity in canopy architecture, photosynthesis, and water-use efficiency in a cowpea magic population

Authors: DIGRADO, ANTHONY - Oak Ridge Institute For Science And Education (ORISE); MITCHELL, NOAH - University Of Illinois; MONTES, CHRISTOPHER - University Of Illinois; DIRVANSKYTE, PAULINA - Oxford University; Ainsworth, Elizabeth - Lisa

Submitted to: Food and Energy Security
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 7/3/2020
Publication Date: 8/7/2020
Citation: Digrado, A., Mitchell, N.G., Montes, C.M., Dirvanskyte, P., Ainsworth, E.A. 2020. Assessing diversity in canopy architecture, photosynthesis, and water-use efficiency in a cowpea magic population. Food and Energy Security. 9(4). Article e236. https://doi.org/10.1002/fes3.236.
DOI: https://doi.org/10.1002/fes3.236

Interpretive Summary: The greatest population increase over this century is expected to occur in Sub-Saharan Africa where large yield gaps currently persist. It is therefore important to develop high yielding crops adapted to this region. Cowpea (Vigna unguiculata) is an important crop in Africa, and in this study we screened 50 lines from the multi-parent advanced generation inter-cross (MAGIC) population for canopy architectural traits, canopy photosynthesis and water-use efficiency. We then used statistical models to relate canopy architectural traits to photosynthesis. The results suggest that the light environment within the canopy was a limiting factor for canopy CO2 assimilation. The width of the canopy relative to the total leaf area of the canopy was associated with greater canopy photosynthesis especially in canopies with high biomass. Canopy water-use efficiency was determined by canopy photosynthetic activity indicating that optimizing the canopy will also contribute to improving canopy water-use efficiency. These results are discussed in the context of improving cowpea yield for the Sub-Saharan African region.

Technical Abstract: Optimizing crops to improve light absorption and CO2 assimilation throughout the canopy is a proposed strategy to increase yield and meet the needs of a growing population by 2050. Globally, the greatest population increase is expected to occur in Sub-Saharan Africa where large yield gaps currently persist; therefore, it is crucial to develop high yielding crops adapted to this region. In this study, we screened 50 cowpea (Vigna unguiculata (L.) Walp) lines from the multi-parent advanced generation inter-cross (MAGIC) population for canopy architectural traits, canopy photosynthesis and water-use efficiency using a canopy gas exchange chamber in order to improve our understanding of the relationship among those traits. Canopy architecture contributed to 38.6% of the variance observed in canopy photosynthesis. The results suggest that the light environment within the canopy was a limiting factor for canopy CO2 assimilation. Traits favoring greater exposure of leaf area to light such as the width of the canopy relative to the total leaf area were associated with greater canopy photosynthesis, especially in canopies with high biomass. Canopy water-use efficiency was highly determined by canopy photosynthetic activity and therefore canopy architecture, which indicates that optimizing the canopy will also contribute to improving canopy water-use efficiency. We discuss different breeding strategies for future programs aimed at the improvement of cowpea yield for the Sub-Saharan African region.