David Van Tassel, Lead Scientist, Perennial Oilseeds
David Van Tassel, lead scientist in perennial oilseeds began working at The Land Institute immediately after completing a PhD in Botany at the University of California, Davis. His main current focus of research is silphium.
What brought you to TLI?
When I was finishing up my PhD, I realized that I really wanted to work with plants and not just with test tubes, DNA, or cells. Also, I’d always had an interest in sustainable agriculture. Back then, you’d probably call it agricultural development or appropriate development, especially for other countries. I’d been very influenced by a film I saw in geography called, “The Children of Peru.” It was about the native Peruvians growing potatoes and how there were very simple things that would improve their lives like reducing the number of potatoes that just rotted. It really inspired me that there was a need for agricultural change and innovation. But at the same time, I was realizing that agriculture here in this country was unsustainable and needed changes.
I had an experience in college – I went to Africa on a school trip and visited some colleagues of my parents. They were missionaries but also working on environmental and agricultural projects. I came to realize at that time that probably the last thing that people in other countries needed was some city kid, like me, coming and telling them what to; in some cases just teaching people things they already know but for one reason or another (often political or social) can’t put into practice. My conclusion was it would be better to work on fixing our agriculture instead of telling everyone else how to do theirs.
Back to the end of my graduate work: I started looking around for ways to get back into sustainable agriculture types of research opportunities and had by that time married. My wife’s father-in-law was a professor at Friends University in Wichita, and he always brought his students to The Land Institute. So, he told me about TLI and that’s how I got connected. I inquired if there were any positions and something came up – I was very lucky.
When you came here, were you one of the earliest researchers?
Of the people here now, yes, but there had been [plant breeders] here long before me. When I first came, the one ecologist I overlapped with for a couple months, John Piper, moved down to Bethel College. Marty Bender [now deceased] and I were the only researchers for a time. It was kind of a low point in the research staff, at least in numbers. And things like the greenhouse had fallen into disrepair – it couldn’t be heated or cooled when I first got here.
I heard you were growing plants in the bathtub at the Krehbiel House for a while?
Yes, I did have a greenhouse light in there at one point because at least the restroom didn’t freeze in the winter or get too hot in the summer!
Stan Cox mentioned he came not long after you, and you both divided up the work?
He’s being kind. Pretty quickly I realized that he knew way more about plant breeding, so I kind of worked as his technician for a couple years. I worked a lot on the sorghum, and we were both involved in growing out some of the Kernza® before Lee [DeHaan] came. We were just starting to look at it. Then Lee really took that over and accelerated it greatly. We messed around with many different things. Even before Stan had come, I hadn’t really settled on any one crop to work on – it was overwhelming. After a while, I kind of just arbitrarily picked Maximilian sunflower because there had been this idea that there were these several “star species”—the top candidates to become perennial grains: eastern gamma grass, sorghum, Maximilian sunflower, Illinois bundleflower, and then mammoth wild rye. Stan and I shared the opinion that eastern gamma grass would be hard to improve as a grain because it produces rather flimsy stalks, and it would be hard to imagine how, even if you made it produce five times more seeds, that it wouldn’t just fall over and break. The mammoth wild rye looked impressive, it had huge heads, but it had a lot of sterility problems. It seemed like the pollen was getting killed in the heat.
Does that mean you would have to keep replanting it?
Well, you really can’t breed if you can’t get seeds or hardly any seeds. The sorghum, of course, Stan picked up, and it seemed like the other good option would be Maximilian sunflower. In retrospect, I realized there really hadn’t been a serious evaluation of its potential. It grows well, establishes quickly, and looks impressive, but it isn’t very drought tolerant, and it has a lot of insect problems (as does silphium.) I worked on Max [Maximilian sunflower] for many years and got gradually disillusioned with it, although I also still feel very sad about abandoning it. But in about 2012 or 2013, I switched over almost completely to silphium. I had been planting out silphium plants and kind of looking at them and bringing that along since about 2002 or so as a back-burner project. Max is not necessarily a bad option for someplace — maybe Canada, where they don’t have the heat and drought in the summers that we do. You wouldn’t need such a deep-rooted plant.
Is the drought tolerance mainly why you’re leaning towards silphium?
Yes, that’s the main reason. It seems to me that being perennial isn’t enough; it [the plant] should have other good qualities like being drought tolerant or stress tolerant in general. Max has very small seeds and I did have some success in increasing their size, but when you start off with extremely small, even doubling is still small. Silphium starts out with seeds that are much, much bigger than those of Max, so it’s just easier to work with. Also, it’s a little more predictable in its growth form. Max can be either short and terrible in a dry year, or humongous in a wet year. Silphium is a little more predictable in its height and branching pattern, so it makes it more attractive to farmers, and easier to work with.
You don’t have to continually adjust your harvesting height?
Right.
You talk about using silphium as an oilseed – do you predict that at some point you will be using it for food, like sunflower seeds?
The actual market for sunflower seeds as a snack or a direct food (confection-type sunflowers) is pretty small. More sunflowers are used for oil, so it’s probably the best target right now. I would like to think that we could maybe make some other byproduct from it, because the seeds do have a lot of protein. As we get the oil content higher, that may go down, but it seems to me we ought to be able to use that protein for something. At the minimum, you can feed what’s left over after you press oil to animals. But I dream about being able to use that protein to make something kind of like tofu, not from soybeans, but from silphium. I think food science people could do a lot with it.
You’re growing it different places globally – is South America the main other location right now?
Yes, currently, and it’s still very small. A couple farmers in Argentina have little test plots and then my collaborators, Alejandra, Damien, and Luciana, are doing some basic science. I need to expand the breeding side of it because the plants grow well there because there’s no pests and diseases of silphium in that area, whereas my stuff up here is just getting hammered.
I’ve expanded how much I’m growing out in Colby, Kansas, which has lower humidity. So, I’m hopeful that we’ll have fewer problems there.
Is the humidity part of the problem with the moths?
Not so much the moths, but the fungus problem. The [Eucosma] moths may be fewer because there isn’t much silphium growing there naturally. It’s a little too dry. Different plants grow out in western Kansas. So, we’ll see.
I read you were looking at different latitudes for growing it. Have you found much difference in growth between here and South America?
Mainly that they grow a lot better in South America because of not having the pests. We did have some plots up in Wisconsin with Organic Valley, and I didn’t think much of it would survive; it was Kansas-adapted stuff. It’s a very cold place: up on top of a hill in a cold part of a cold state, and the year after we planted it they had one of their coldest winters. Yet almost all of it survived. We had been planning on having to breed for cold tolerance and it turned out we didn’t have to. Since then, we’ve planted some in Vermont, Minnesota, and other places. It seems like winter kill is one of the few problems we don’t have, so that’s encouraging. We have a plot in Texas, speaking of different latitudes, and apparently it’s also fairly humid down there and it’s getting a lot of fungus problems, too. It seems like it’s more about whether we have these insects and diseases rather than heat and cold. Those don’t seem to be the problem. It’s hard to separate all that stuff out when the plants are looking terrible because of fungus; it’s hard to know what they would look like if they weren’t diseased.
You mentioned on the TLI silphium page that it could be a good candidate for intercropping because it doesn’t appear to be very competitive. What do you mean by that?
It doesn’t seem to spread. That’s all relative. Plants are always competitive with each other; there’s no free lunch. So, you can’t just expect that a plant won’t take water or nutrients. It will. And if it shades smaller plants, they won’t be able to do as much photosynthesis. But it just doesn’t form a real thick stand, and it doesn’t spread.
When you were talking about intercropping, did you have anything specific in mind to grow it with?
Brandon [Schalutmann] was just talking to me about trying a whole panel of legumes as potential intercrops. We’ve tried it with some, and either they hardly grew at all—not in meaningful quantities to add much to the system—or they did great in the spring when silphium came out, and then smothered the silphium. So, we haven’t found quite the right combination there. For many years, I have been growing plots, not all the time, but off and on, in grass. I’ll plant grass between rows of silphium or I’ll plant grass and then plant silphium into that grass. I know that can work. The grass is competitive with silphium for nitrogen and water, presumably. Although the silphium is probably getting water from below where the grass root zone usually is, so probably when it comes down to water, the silphium will be alright. But again, there’s no free lunch and if there’s a certain amount of nitrogen, then they’re going to have to split it up.
The root pictures of silphium are very impressive.
What makes me think it might be good for intercropping is that it has a very different kind of root system than any of the grasses, the sorghum, Kernza, and a lot of our legumes. There are some that are – alfalfa has very deep tap roots similar to silphium, but not all legumes have that.
In the sunflower family, are there other crops that you’re looking at?
I’m really focusing on silphium. I have tinkered around with some of the other silphium species and some of them have traits that I like: in one case even bigger seeds and leaves that stay low down to the ground, which would make it a lot easier to harvest the seeds without getting a lot of leaf material in the harvester. I’ve continued to observe some of those. There’s another silphium that’s used in Europe and in Asia as a forage or bioenergy crop. It’s called cup plant. And we have hybrids with it, we’ve been crossing with it. It has some traits that we like: it has some disease resistance. It has lots of heads – very small heads with very small seeds – but there are more of them. So, if we could get the best of both, that would be great. We could have the big seeds and big heads of my silphium and the many heads of cup plant. I think there are probably other good oilseed options. But I don’t really have time to explore them.
Have you had any discoveries in the past few years that you would point out as ones that really helped you move forward or that you would say are significant?
I guess one thing would be that I have found some plants with heads that are quite a bit bigger than others. I’ve crossed those plants with each other and with plants that are good for other things. I don’t have a big group of them yet that are like that, but it gives me some hope that silphium could change just like what happened in [annual, domesticated] sunflower. I don’t think we need to get to the size of the head of annual sunflower, but bigger would be somewhat better. We have seen that if we cut the stems down at certain times of the year they’ll branch out, and then we can often grow much shorter and have the heads more at the same height, the way they branch out. And that might be an effective and simple way to manage the height. It’s not unheard of for perennial crops to have to be managed like that. You may have to prune them—like orchards in a sense–to get that better branching pattern and height. I’m going to be testing that, and other people are testing that too. What I expect to see is that some plants don’t like it at all and kind of fall apart after you do that. And others can handle it very well and give you really good results. So, if that’s true, then we need to start trimming all of them and breeding whichever ones can handle it.
Do you do genetic testing on your plants the way the perennial wheat and Kernza programs do?
With our collaborators at the University of Minnesota, we’ve made a very simple genetic map using DNA markers. That needs to be improved and repeated. We need to do some more DNA sequencing. The challenge is that it’s a very big genome, and that makes it very expensive. I think there are other ways to develop markers that we can use for breeding. For example, we may be able to sequence RNA instead of DNA, because there’s much less RNA. I don’t anticipate getting to quite the level that Kernza is where they sequenced the whole genome. I don’t know that we need that. We’re moving in that direction but we’re still in the early stages.
Do you have any specific goals that you hope to achieve within the next 5-10 years that you are working towards?
We were really hit hard by rust, which is a kind of fungus, and with Kathryn [Turner]’s help, we have found some resistant plants. Now, after a few years of really focusing on that, I have quite a lot of lines and groups that have at least some rust-resistance. So, I feel hopeful that we can find, use, and combine that with the genetics that give better yields. The ones that are resistant aren’t always the best ones for yield, so we have to combine those things. I need to wrap that up to where almost all the stuff that we’re giving to people, or that we are using, is rust-resistant. That would be one goal.
Another goal would be to likewise adapt to this moth that’s become a big problem. We have seen that some plants can produce seeds, even though they have the moth, and quite how and why that happens is not clear, but it’s somewhat encouraging that some plants seem to be able to do that. And so, another big emphasis is trying to understand that and start breeding for it.
Then, if we can control the height, that would be another one. Figuring out how to harvest [is another goal], whether that means breeding the seeds to be bigger and heavier, so they don’t just blow out the back of the combine or coming up with some different way to harvest, because that’s a real problem. The seeds are flat and blow very easily. They’re big and designed naturally to spread by wind, so that makes it a real problem for cleaning them. We need to figure out how to harvest and clean the seeds a little more efficiently, and that may require both breeding and equipment engineering.
And then also to be able to get to the point where we could use some of these genomic tools like genomic selection that Lee has been investing in. It’s very promising for accelerating breeding, and breeding for certain things that otherwise would be too expensive to measure routinely, and so I would really like to be able to start to use that in five years or so, at least at some level.
Check out the other interviews in the series!
Interview with a Plant Scientist: Stan Cox, Perennial Sorghum
Support the work of David and other plant breeders at The Land Institute.