The first International Wheat Congress was held in the heart of the Canadian Prairies in July 2019, the result of a merger of the International Wheat Conference and the International Wheat Genetics Symposium.

The small town of Saskatoon hosted more than 900 wheat researchers, breeders and other industry representatives for five days of presentations, networking and field tours.

There were a number of new discoveries including how wheat is responding to increasing night temperatures, how to make wheat more drought tolerant and some developments in the characterisation of the wheat genome.

The Australian wheat community was well represented, with eight Australians invited to present their research, demonstrating the high regard for Australian wheat research on the international stage.

The congress was an important opportunity to identify potential collaborations with global experts in fields that are relevant to GRDC's Key Investment Targets.

There were a number of new discoveries, including how wheat is responding to increasing night temperatures, how to make wheat more drought-tolerant and some developments in the characterisation of the wheat genome.

Wheat genomics

The sequencing of the wheat genome has led to a boom in research that is exploring uses for this extensive resource.

An exciting development has been the discovery of a special type of genomic shuffling, called gene conversions, in which genetic material on an intact chromosome is used to repair a related gene on the same or on a different chromosome that contains a break in the DNA. This swap of genetic material results in the recipient acquiring the same DNA sequence as the donor.

Research has found that gene conversions are common in wheat, but rare in model plant species used in laboratory experiments and other species more generally.

These gene conversions also tend to be much larger in wheat and are more evenly spread across the chromosome than traditional events that result in DNA exchanges between chromosomes.

This discovery is important as it provides a mechanism that can be manipulated in pre-breeding research to increase the rate of gene discovery as well as in breeding to maximise effective population size.

There has also been significant progress in the 10+ Genome Project, which aims to sequence at least 10 different global wheat cultivars.

Two Australian cultivars, Lancer (PBR) and Mace (PBR), have been included in this set of 10 and show significant differences in sequence to the reference genome, Chinese Spring.

As sequencing technologies continue to decrease in cost, the number of varieties in the set will increase. This growing source of information will increase the speed with which researchers can determine the genetic basis of key agronomic traits in wheat.

Response to increasing night temperatures

Modelling from an Argentinean group led by Daniel Miralles, along with CSIRO collaborator Dr Fernanda Dreccer, has looked at the effect of increasing night temperatures on wheat yield.

In Argentina, climate change is asymmetrical, with the nights getting warmer faster than days.

To test the effects of warmer night temperature on yield, special heated tents were placed over plots in the field from stem elongation to flowering. The tents raised the temperature about 3.9°C above ambient during the nights only.

For every degree increase in temperature, the average loss in grain was 7 per cent. Development was also sped up and there was a decrease in grain number per square metre due to a reduction in spikes.

If the same treatment was applied during grain filling, there was a smaller decrease in yield of 3 per cent per degree of increased night temperature. Again, the duration of grain filling was reduced leading to a decrease in thousand kernel weight.

Modelling has indicated that asymmetric warming may have impacted wheat and barley potential yields in the Argentinean Pampas as much as 9 per cent for every degree of warming over the past five decades, linked to crop cycle shortening.

Physiological studies at the International Maize and Wheat Improvement Center (CIMMYT) in Mexico, led by Gemma Molero, looked at how different varieties respond to increased night temperatures.

The group found that yields were higher in lines that were cooler at night, indicating they had a higher rate of transpiration.

They also found that lines containing wild relative genetics were more likely to have a lower canopy temperature under heat stress, indicating the presence of genetic material useful in improving heat tolerance.

Understanding drought tolerance

Interesting developments are also underway that help understanding of how plant transpiration responds to the environment, which could be used in the future to improve the water use efficiency of wheat.

Transpiration is the process by which plants lose water from pores on the leaf surface, which have to open to allow in the carbon dioxide required for photosynthesis.

A group from the University of Minnesota, led by Walid Sadok, investigated how transpiration rate varied across different wheat varieties in response to different vapour pressure deficits between the air and leaf (VPD).

The group detected a 2.9-fold variation in transpiration rates across different wheat varieties worldwide.

While the transpiration rate of Minnesota varieties did not respond to changes in the VPD, all the Australian varieties showed a segmented response where they have higher transpiration rates when conditions are humid, but reduce water loss when conditions become drier.

A modelling case study targeting Tunisia indicated that different transpiration strategies would have benefit in different regions of Tunisia, with a segmented response expected to increase potential yield by up to 30 per cent in some parts of Tunisia.

Another group, led by Tracy Lawson at the University of Essex, identified differences between wheat lines in the speed at which transpiration responds to changes in light.

In field conditions, where light intensity can change rapidly with cloud cover and as wind passes through the canopy, slow responses can limit the amount of carbon fixed by the plant and instantaneous water use efficiency (the amount of carbon fixed per unit of water lost).

Understanding the genetic control of this process could lead to greater efficiencies in crop water use, which could be considerable when combined across a season.

The next international Wheat Congress is scheduled for 2021 in Beijing.

More information: Pip Wilson, pip.wilson@grdc.com.au