Powdery Mildew on Grapes

Light Bulb Hunting: Student Spotlight on Soon Li Teh

It’s a fungus that can devastate an entire grape crop from leaves to fruit, eliminating entire yields: powdery mildew. The fear of powdery mildew leads to frequent fungicide applications, but graduate student Soon Li Teh (Applied Plant Science, Ph.D.) hopes for a better way to control it. Advised by professors Jim Luby and Adrian Hegeman, he is combining DNA marker-assisted breeding with metabolomics to speed up the selection process towards powdery mildew-resistant wine grape varieties.

Soon Li Teh with the grapes he's doing research on

Soon Li Teh’s time at the U has not only cultivated his research skills, but he has discovered a passion for teaching as well and was awarded the CFANS Graduate Assistant Teaching Award this year. Teh is eager to explain his work to others, and works hard to make sure they understand even though it can be complex. “I made a point that I must be able to communicate what I’m working on. Otherwise it’s pointless to work on it.”

Originally from Malaysia, Teh has spent the last eight years studying in the United States, first getting his undergraduate at the University of Wisconsin–Madison before coming to the U. As many as 75% of undergraduate students change their major at least once, but Teh has always been confident that he was on the right path. “As a freshman, I was very certain that not only was I going to go into plant breeding and genetics, I was going to get a Ph.D. That fire has never really died.” His dual degree in agronomy and biochemistry inspired him to pursue a research project that combined those two areas, ultimately setting his sights on solving the problem of powdery mildew in wine grapes. “I was interested in understanding disease resistance beyond the DNA level; do we have any information from the metabolite level that can help us understand why plants are resistant or not to powdery mildew?”

Finding this information isn’t easy though. “It’s like trying to find a broken light bulb in the basement of one house somewhere across the entire United States,” says Teh, using an analogy coined by geneticist Francis S. Collins. In his case the light bulb is the exact area(s) of the genome that determines whether or not a grape vine is resistant to powdery mildew.

The first step in finding that light bulb is through DNA mapping. “We have about 125 individual plants in the vineyard at the Horticulture Research Center. We gave each of them a score for resistance to powdery mildew from 1–9 and then sent samples off for gene sequencing.” Once he had the gene sequences he could look for patterns in them that mirrored the vines’ resistance scores. These patterns can be turned into DNA markers, and can be used on seedlings to determine if they will be resistant without the cost of growing them for several years.

The genetics portion of his project has already yielded good results: two genetic regions linked to powdery mildew resistance, one of which has been previously reported. However, there’s still a long road before he finds his light bulb. “So far, I’ve identified where the chromosomes are and what the regions are. And that gets me as close to saying it’s in St. Paul, MN. We’re not close to finding the exact spot yet, but closer than we were.”

Moving into the final year of his Ph.D. program, Teh has turned his full attention to the metabolomics portion of his thesis, which will hopefully identify key chemical compounds that make grape resistant to powdery mildew. The process is similar in idea to creating a DNA marker, but at the analytical chemistry level. He runs a sample from a grape vine through a mass spectrometry machine to get a chemical profile of the sample—which can yield thousands of results. By comparing the chemical profiles of vines that are and are not resistant to powdery mildew, Teh can start pulling out patterns that indicate a vine’s resistance. The results of his metabolomics research aren’t available yet, but he is optimistic about the results he’ll get this year.

His research is still ongoing, but Teh is already thinking towards his future graduation, though he isn’t quite as certain as when he was a freshman. “It’s hard, because I’m very passionate about both research and teaching. So honestly, right now I have no idea if I’ll end up in academia, or industry, or teaching at a small college,” he says. “The good thing is my wife and I aren’t bound to any specific country, so the next step might be another adventure.”

Article written by Echo Martin
Header image, "Powdery mildew of grape" by Maccheek is licensed under CC BY-SA 3.0

 

June 24, 2016

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