Wheat scab has been described as a wheat-industry-threatening disease. Essentially this fungus thrives on corn stubble. When you plant wheat into corn stubble, the fungus can jump into the wheat flower and causes the disease.
All the wheat varieties essentially are susceptible to this disease. It turns out that the only source of resistance is in the Chinese landrace Sumai 3. All the other world's landraces of wheat lack this resistance. We essentially cloned the DNA of this variety into bacteria. There were millions and millions of clones and eventually, through painstaking work, identified a small piece of DNA, which turned out to be, when you introduced them to wheat plants, made them resistant.
So we essentially identified this gene, and this gene hunt has been ongoing for the last 20 years. We have been fortunate to be the first one to get it. Now that we have this gene, we can diagnose whether any variety has this resistance gene or not. So number one, identifying this gene is very useful as a diagnostic asset. It's a perfect marker. Number two, we can now play around with this gene. We can forward express this gene. We can put in promoters that make the plant more resistant. We can also use the gene sequence to fix susceptible genes in other cultivars with a technique called genome editing.
Figure 1. Automated pipetting for DNA analysis.
Figure 2. Examining chromosome constitution of wheat.
Generally, if a plant resists a disease it's a very long pathway with many genes involved. Now that we know one piece of the puzzle, we can uncover the whole pathway. And that will even suggest many more approaches and many more targets where we can intervene and make plants resistant to a disease.
Bikram Gill, Distinguished Professor of Plant Pathology