Wheat and barley are incredibly diverse

The grains we use for bread and beer have thousands of years of history. Now, researchers are one step closer to understanding their diversity.

Two international teams have made a significant leap towards defining the mind-bogglingly complex core genes in all barley and wheat species – an effort that will greatly boost the ability to breed them. 

The research takes the next step beyond using a single genome as a genetic reference, and begins to construct a massive, encompassing encyclopedia of genes.

“Modern wheat and barley cultivars carry a wide range of gene variants and diverse genomic structures that are associated with important traits, such as increased yield, drought tolerance and disease resistance,” says Peter Langridge from Australia’s University of Adelaide. 

“This variation cannot be captured with a single genome sequence. Only by sequencing multiple and diverse genomes can we begin to understand the full extent of genetic variation, the pan genome.”

Langridge is a co-author of a paper describing the wheat study, which was led by Curtis Pozniak from Canada’s University of Saskatchewan. The barley study was led by Nils Stein from Leibniz Institute of Plant Genetics and Crop Plant Research, Germany. Both papers are published in the journal Nature.

The two projects involved more than 100 researchers from Australia, Canada, China, Germany, Japan, Mexico, Israel, Switzerland, Saudi Arabia, the UK and the US.

There is still genetic variation between plants of the same species, which is how we have different strains or varieties of crops. The full collection of genes found in all these species is called the pan genome and provides necessary knowledge to overcome challenges like drought, heat, climate change and food insecurity. 

However, the genomes of barley and wheat are large and complex: they are two and six times bigger, respectively, than the human genome and much more prone to genetic mutation.  

Wheat, in fact, has one of the most complex genomes known to science, and was a seemingly impenetrable fortress before modern genomics. This has been a huge hurdle when sequencing the genomes of specific varieties and has caused this research to lag other, more simple crops.

“Advances in genomics have accelerated breeding and the improvement of yield and quality in crops including rice and maize, but similar efforts in wheat and barley have been more challenging,” says Langridge. 

“This is largely due to the size and complexity of their genomes, our limited knowledge of the key genes controlling yield, and the lack of genome assembly data for multiple lines of interest to breeders.”

Previously, wheat genomic data was based on the genome of an old Chinese variety, but plants don’t grow the same in different environments, so that genome only provides limited insights. For example, many varieties of European wheats will not survive an Australian summer because they have the wrong genes. 

Now, with varieties in Australia, Asia, North America and Europe, breeders have a more accurate and global representation of wheat genes that help them grow in specific environments.

 “The 10 varieties represent a significant portion of the worldwide variety of wheats. The genome data, which are freely available to all interested parties, constitute an important resource for humanity,” says Beat Keller, from Switzerland’s University of Zurich.

The researchers also found that barley strains are very diverse and experienced many significant mutations over their convoluted evolutionary history that spanned millennia. Previously, these mutations had gone unnoticed, but could actually prevent some traits from being inherited when different varieties are bred together. This highlights how important this genomic data is.

“The description of such large genomic inversions in barley is new,” says Nils Stein. “They can play a decisive role in the breeding process as they might prevent recombination, thus making cross-breeding for desired trait combinations impossible.”

“We have created a new knowledge-base and opened up a treasure trove of new information for breeding.”