Photosynthesis is the trait now being targeted globally to deliver future yield gains in bread wheat. Crucial to these efforts is the ability to measure and compare (phenotype) photosynthesis efficiency among the thousands of lines needed in breeding programs.
The work is building on an earlier Australian development, an analytical light tool called hyperspectral reflectance (HSR). This became the basis of a fast, high-throughput, paddock-deployable tool which can measure several key aspects in photosynthesis biochemistry in seconds.
Now, researchers working within the International Wheat Yield Partnership (IWYP) have used HSR to screen mapping populations that allow the detection of DNA markers associated with photosynthesis traits.
The ultimate goal is to put a bigger photosynthesis engine in the leaf while ensuring the plant has a suitable throttle to extract optimal productivity gains. – Professor John Evans
A key research focus was a population derived by crossing Seri and Babax cultivars, previously used to study drought-adaptive traits.
In this new project, HSR has proved to be a robust phenotyping tool for plants grown both in high-throughput glasshouses and in the field in Australia and at the International Maize and Wheat Improvement Center (CIMMYT) in Mexico.
In parallel to this effort, UK-based researchers accepted the challenge to map differences in photosynthesis traits at the genetic level.
A new tool
This IWYP project, “Using Next Generation Genetic Approaches to Exploit Phenotypic Variation in Photosynthetic Efficiency to Increase Wheat Yield (IWYP64)”, is headed by Professor Anthony Hall of the Earlham Institute in the UK and also involves researchers in Australia and Mexico.
The results amount to the maturation of an important new phenotyping technology. – Professor John Evans
Among them are professors John Evans and Robert Furbank of the Australian National University, both of whom are world-leading specialists in the study of crop photosynthesis.
Part of the IWYP64 team at the IWYP meeting in Obregon, Mexico, 2017. Left to right: John Evans (ANU), Cristina Sales (Lancaster), Anthony Hall (Earlham Institute), Elizabete Carmo-Silva (Lancaster), Ryan Joynson (Earlham Institute), Gemma Molero (CIMMYT), Hammad Khan (ANU). Not shown are Robert Furbank (ANU), Matthew Reynolds (CIMMYT), Martin Parry (Lancaster).
Professor Evans says photosynthesis is such a new target for breeding that foundational work was necessary to develop the ability to screen and select for photosynthesis-related traits.
“The key thing here is working up fast and reliable phenotyping abilities to measure traits in the field and, at the same time, to map the surveyed traits genetically,” he says. “This is such a new area that we need to actually demonstrate that there are genetic associations for the traits we are measuring with HSR.”
While work continues on the genetic characterisation, the projects did find that HSR technology is a viable, robust and useful tool to phenotype wheat at the scale necessary to breed for greater radiation use efficiency, even when used by different operators in different continents.
“This project saw the maturation of an important new phenotyping technology,” Professor Evans says. “We now have a new tool to assess and compare wheat germplasm for diversity in photosynthesis traits.”
A new trait
Phenotyping with HSR involves clipping a light-emitting sensor to a leaf. The light reflected from the leaf surface is analysed by a spectrometer, which quantifies the amount of reflected ultraviolet, visible, near infrared and shortwave infrared light.
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