Extra-Resistant Wheat is Created From New Gene Combination
News Jan 23, 2018 | by Ruairi J Mackenzie, Science Editor, Technology Networks
Credit: Mario Waldburger, Agroscope
A novel combination of gene variants that bestow resistance to a common fungal blight may help farmers grow more resistant wheat, according to new research published in Theoretical and Applied Genetics.
Powdery mildew affects the aerial parts of plants, invading the plant’s surface and breaking down the tough cell wall that surrounds individual plant cells. It then extends a long appendage, called an haustorium, which drains nutrients from the plant. Powdery mildew infections can reduce crop yield by up to 30%.
Resistance Genes Self-Sacrifice Infected Cells
Several years ago, researchers at the University of Zurich identified a gene that gives resistance against powdery mildew to the plants that contain the gene. This gene, named Pm3, codes for a receptor that recognises a protein produced by powdery mildew. When the mildew attempts to drain nutrients from a plant cell, the Pm3 receptor triggers the self-sacrifice of the affected cell, protecting the rest of the plant from fungal attack. Different versions of the Pm3 gene, called alleles, are receptive to different powdery mildew proteins.
Previously, Dr Beat Keller and his team had identified these variant resistance genes in wheat strains taken from around the world. These beneficial genes were then added to Bobwhite wheat, which does not have any Pm3 genes and is therefore vulnerable to powdery mildew. Four different resistance genes were added to Bobwhite, creating four newly resistant strains. In the current research, Keller’s team bred two of these strains together, meaning the resulting crop offspring had two different versions of the resistance gene in their genome, one from each parent.
Fungal Resistance Increased by Transgenes
The successfully finding from the study is that both of the inherited alleles performed as well in the offspring as they had in their parents, meaning the offspring had an increased total resistance to the fungus. In a recent press release, lead author Teresa Koller said “The improved resistance against powdery mildew is the result of the increased total transgene activity as well as the combination of the two Pm3 gene variations.”
The crops were carefully monitored over two seasons from 2015-17 for any negative side effects of the new genes. The increased resistance gene activity did not have any negative impacts on the crops’ yield or growth.
These findings contrasted with results produced in the same study from seedlings grown in greenhouses, and shows the value of in-field testing. The study has increased knowledge of how crops fight off infections like powdery mildew and can also be applied in practice, as these varieties can now be crossbred traditionally to produce stronger, more resistant wheat.