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Davis, California

Sunday, May 19, 2024


UC Davis is one of two schools in the country with a nematology department. What’s a nematode, you ask? Professor Valerie Williamson can not only tell you that a nematode is a microscopic worm, she can also tell you its DNA sequencing and the massive impact it has on the agricultural world today. Williamson is a professor of nematology, focusing her research on plant parasitic nematodes – the cause of over $50 million of plant damage in the U.S. The California Aggie sat down with her to chat about nematodes, her research and even her taste in produce.


Why study nematodes?

Well, lots of reasons. They’re really interesting. They’re one of the largest phyla of animals in the whole world. There’s a lot of free living [nematodes] that affect the soil and environment; there are animal parasites that have caused lots of diseases in animals, including humans.

[For instance] in Africa, you’ve probably seen Elephantitis in your biology books, which is caused by a nematode. Probably a third of the world’s population has nematode infections-mostly developing countries. So they’re very common.


What kind of nematodes do you research?

I study the ones that infect plants. They’re a big problem because most of them cause $50 to $100 million in damage worldwide. For example, I work with tomatoes, and nematodes can be a big problem on tomatoes.

In fact, a lot of home-growers have nematodes on their tomatoes. Sometimes if your tomato isn’t growing very well, you can pull it up and find these big knots on the root – that’s due to nematodes.

So it’s a pretty big problem around here – especially if you have heirloom tomatoes because they don’t have resistance. In agriculture in California, some of the ways they control these nematodes is that they put pesticides on the fields like Methyl Bromide, which is being banned because it’s damaging the ozone layer. One of the uses of [Methyl Bromide] is for killing the nematodes in the soil. So right now, there’s a lot of concern about how we’re going to kill these nematodes without harming the environment. A lot of the things that kill them are really nasty and toxic.

The other thing bad about [nematodes] is that they kill everything in the soil. And there are good things in the soil that can help kill a nematode. So it’s difficult to find a sustainable way to control [what is killed in the soil].

I’m working more at the basic research biology end of that, so in order to figure out better ways – instead of hitting [a nematode] on the head with a hammer using a pesticide, you have to understand the organism better. So I’ve been working on plant parasitic nematodes, trying to understand how they work and if there’s any weakness in their system, [so] we can figure out a control that we can just target instead of the good guys.


So nematodes have a lot of impact on California agriculture?

Yeah, they have a lot of impact. I study the root knot nematode which affects not only tomatoes but also just about everything. Fruit trees, grape vines, cucumbers, melons and lots of other plants. There are other nematodes that have a big impact on trees, like walnut trees, that are causing a lot of damage.


Does all this research on food ever make you hungry?

Well, I like a good tomato. But the problem is that the heirloom tomatoes really taste better than the ones you buy in the grocery store, but [heirlooms] are susceptible to nematodes! Sometimes when I go to the grocery store and look at the organic carrots, I check the root at the bottom for bumps in there. I know that inside of those little bumps there’s a nematode, so sometimes that makes me not hungry. You can eat them and it doesn’t hurt you at all, its just an unappetizing thought.


So you eat organic food?

Only when it’s on sale. I don’t go out of my way for it because I think it tends to be overpriced. Although sometimes I buy it at the farmers market because I know the people who grow it locally take good care of their land.


Who is your favorite scientist?

My husband! He’s a virologist here.


What do you teach?

I teach molecular biology lab techniques, so it’s a lab course in animal genetics. It’s a course that a lot of undergraduates take. I also teach a course in agricultural biotechnology that discusses transgenic [genetically modified] plants and the pros and cons of them.


Have you been able to form a relationship with the students in your lab classes?

Oh yeah, we talk all the time! The interaction with the students is what I value most about being a professor. Both classes I teach are relatively small and I get to interact individually with the students and I really like that. I like that a lot better than standing in front of 100 students lecturing. I like to talk to them a lot more individually; it’s more fun.


Do you think the pros of transgenic plants overweigh the cons?

[Yes,] I think so. There’s a lot of issues with them because of the way they’ve been developed by these big companies. In general though, they’re a good idea because you can reduce pesticides.


Have you ever had a bad run-in with a transgenic plant protester?

No not really – other people have. When they first sold genetically modified tomatoes, they sold them in a grocery store in town and protesters came and dropped tomatoes in the parking lot. In other places there’s big controversy, but in Davis since we’re an agriculture school there’s not so much.


So when you were a kid, what did you want to be when you grew up?

I always liked biology – I never knew exactly what it was – but I did think about being a veterinarian. And I wanted to become a medical technician. But research has always been my point of interest.


Do you have pets?

Yes, I have two dogs. They’re pound rescues. They’re really nice pets.


Where are you from originally?

New Hampshire. I came to Davis for graduate school. I did my Ph.D. work at Davis and my undergraduate work in Boston. I went to Seattle for my post-doctoral and then came back to Davis. A lot of people come back to Davis.


Which has been your favorite place?

I like being right on the ocean, so probably Bodega Bay. We’re planning to retire to Bodega Bay.


Are you retiring soon?

Well, we just sequenced a [nematode] genome, so a lot of possibilities have opened up that we didn’t know about before. That makes it hard to leave.


LAUREN STEUSSY can be reached at features@californiaaggie.com.


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