Scientists further cowpea research--boosting canopy CO2 assimilation, water-use efficiency

Date:
August 17, 2020
Source:
Carl R. Woese Institute for Genomic Biology, University of Illinois
at Urbana-Champaign
Summary:
New research aimed to determine how much variation exists within
diverse cowpea lines' canopy photosynthesis. Results from this
study suggest that by optimizing canopy structures, researchers
could increase cowpea yields, and yields across other crops,
to improve our global food security.



FULL STORY ========================================================================== Crops grow dense canopies that consist of several layers of leaves --
the upper layers with younger sun leaves and the lower layers with older
shaded leaves that may have difficulty intercepting sunlight trickling
down from the top layers.


==========================================================================
In a recent study published in Food and Energy Security, scientists
from Realizing Increased Photosynthetic Efficiency (RIPE) aimed to
understand how much variation exists within diverse cowpea lines in
light absorption and carbon dioxide (CO2) assimilation throughout the
canopy. This information can ultimately be used to design more efficient canopies -- with greater CO2 assimilation and water-use efficiency --
to increase yields.

RIPE, which is led by the University of Illinois, is engineering crops to
be more productive by improving photosynthesis, the natural process all
plants use to convert light energy to produce biomass and yields. RIPE
is supported by the Bill & Melinda Gates Foundation, the U.S. Foundation
for Food and Agriculture Research (FFAR), and the U.K. Government's
Department for International Development (DFID). One of the target crops
of the RIPE project is cowpea.

Cowpeas, commonly known as black-eyed peas in the U.S., are one of the
oldest domesticated crops in the world, responsible for feeding more
than 200 million people per day.

"They are a staple crop in Africa, providing a source of protein for
humans and livestock, and restoration of soil nutrition through nitrogen fixation," said Lisa Ainsworth, a research plant physiologist with the
U.S. Department of Agriculture, Agricultural Research Service (USDA-ARS).

The RIPE team screened 50 cowpea genotypes from a multi-parent advanced generation inter-cross (MAGIC) population for canopy architecture traits, canopy photosynthesis, and water-use efficiency by using a canopy gas
exchange chamber. This chamber was used to measure the rate by which
plants would convert CO2 in the atmosphere into carbohydrates as energy
for growth.



========================================================================== "Since sub-Saharan Africa is the region where important yield gaps
persist, it is crucial that we develop a high yielding crop that can
be easily grown there," said first author Anthony Digrado, a USDA-ARS postdoctoral researcher in Ainsworth's lab based at Illinois. "That is
to say that water-use efficiency should be taken into serious account
when developing new varieties for sub- Saharan African countries that
are challenged by access to water in several regions." The team used
Principal Component Analysis (PCA) models to first group the 50 MAGIC
genotypes into five general canopy architectural types to study plant
traits, including leaf area index, leaf greenness, and canopy height
and width.

This analysis gave researchers the ability to gather an overview of the
traits, or combinations of traits, that could be modified to have the
strongest impact on canopy photosynthesis to maximize growth.

Canopy architecture contributed to 38.6 percent of the variance observed
in canopy photosynthesis. Results showed that in canopies with lower
biomass, the major limitation to canopy photosynthesis was leaf area;
however, in higher biomass canopies, the major limiting factor was,
instead, the light environment. Canopies with high biomass have greater
canopy photosynthesis when leaves at the top of the canopy have lower chlorophyll content.

Overall, canopy architecture significantly affected canopy photosynthetic efficiency and water-use efficiency, suggesting that optimizing canopy structures can contribute to yield enhancement in crops.

"Water-use efficiency refers to the amount of CO2 assimilated by a crop
canopy relative to the amount of water that is lost by the canopy,"
said Digrado, who led this work at the Carl R. Woese Institute for
Genomic Biology (IGB). "The ideal for a crop is to be able to have a
lot of carbon intake without losing too much water." The MAGIC cowpea population that the team used matches this criteria for an ideal crop, especially one to be grown in the drought conditions of Africa.

However, research on how canopy architecture affects canopy CO2
assimilation and water-use efficiency in cowpea continues to be scarce.

"There is still a lot to do to improve cowpea yields and much more
research is needed," Digrado said. "But this work has established
that variation exists that can be used to improve productivity and
efficiency of an important food security crop." The RIPE project and
its sponsors are committed to ensuring Global Access and making the
project's technologies available to the farmers who need them the most.


========================================================================== Story Source: Materials provided by Carl_R._Woese_Institute_for_Genomic_Biology,_University of_Illinois_at_Urbana-Champaign. Original written by Amanda Nguyen. Note: Content may be edited for style and length.


========================================================================== Journal Reference:
1. Anthony Digrado, Noah G. Mitchell, Christopher M. Montes, Paulina
Dirvanskyte, Elizabeth A. Ainsworth. Assessing diversity in canopy
architecture, photosynthesis, and water‐use efficiency in
a cowpea magic population. Food and Energy Security, 2020; DOI:
10.1002/fes3.236 ==========================================================================

Link to news story: https://www.sciencedaily.com/releases/2020/08/200817104300.htm

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