Søren predicts the future of wheat production

18 November 2021
PhD student Søren Gjedde Sommer works on how to evaluate the most drought and heat resistant genotypes of wheat and investigates which physiological traits would be sensible to breed for in the future.

Mankind faces a future with an increasingly unpredictable climate, with more frequent periods of drought, extreme heat and a higher concentration of CO2 in the air. These factors are extremely influential on the health and output of wheat crops, which, with a global production of 760 million tonnes in 2020, is one of the most important foods sources for people.

If, going forward, we have conditions like in 2018, when winter wheat yields were down by 20% in Denmark primarily due to an unusually dry period between May and July, we may have to alter the way we think about wheat production. Historically, the primary focus has been on breeding towards disease resistant high yielding wheat genotypes, but in the future, we might have to prioritise a larger diversity in genotypes. In terms of drought tolerance that may mean genotypes with lower yields potential, but that are on the other hand more tolerant to drought occurrences,’ says Søren Gjedde Sommer.

There exists thousands of wheat genotypes, and there are many parameters on which they can be assessed, but when it comes to heat resistance there are very few methods of conducting evaluations, explains Søren Gjedde Sommer.

The primary goal of my research is to assess the strength of our specific screening method for heat stress. Furthermore, I search for bottlenecks that explain how we physiologically can explain why yields decrease as consequence of heating or drying events. Long term we hope our screening method will prove viable in breeding programs aiming at increasing heat tolerance in wheat grown in temperate regions with no consequence for the yields in seasons with optimal growth conditions,’ Søren Gjedde Sommer says.

Looking into physiological differences
In the first experiment of his project, Søren Gjedde Sommer cultivated two Swedish and an Australian wheat genotype for the purpose of comparing them and identifying their physiological differences. The genotypes were chosen based on a chlorophyll fluorescence screening protocol developed in his research group at the University of Copenhagen. The results gave an insight into the traits that made each type more or less tolerant to heat. For that purpose, he used a gas exchange and fluorescence system for measurements of photosynthesis.

We have a “photosynthesis machine” that lets us control how much water, CO2 and light we expose a plant to and then we monitor the photosynthetic response. In this specific case there was a trend showing that more heat tolerant genotypes had more stomata (leaf pores), and were better at cooling the leaf under high temperature conditions. That can be a good way for it to protect itself against extreme heat, but it can also be a very dangerous exchange for the plant in periods where water resources are also scarce, because it loses water,’ explains Søren Gjedde Sommer.
Currently, he looks into the speed with which certain enzymes metabolize and facilitate the transport of carbohydrates from the leaf to the ear of the plant. Particularly, the activity of the enzyme invertase is interesting to Søren Gjedde Sommer. Originally, he planned to conduct experiments on this enzyme and analyse the results in Changchun, China, where professor Li Xiangnan, who has a strong connection to the Crop Stress Physiology group at the University of Copenhagen, is based. Unfortunately, due to Covid-19, Søren Gjedde Sommer has had to alter those plans and carry out that work in Denmark.

Looking ahead
In the final year of his thesis, Søren will spend a bit less time in the laboratory and more behind his computer writing his dissertation, but also a few articles, of which one will be published soon. During this time, he will also begin to gather all of the threads and provide some foresight.

I hope my research will provide some insight to the top tools available for us in order to breed for crops that are more resilient in response to events of heat and/or drought in the future