To produce the wheat for our bread, sunflower oil for our stir-fries and rice for our risottos, farmers follow a centuries-old practice: plant, harvest, repeat. But annual grain and oilseed crops, which die after one season, have a downside: they can damage soils and water systems and ruin wildlife habitats. That has led some plant biologists to look to wild relatives that are perennials, which live, grow and produce for multiple years. The modern wave of perennial grain domestication is a century old, but only in the last few decades have emerging genetic technologies made it more feasible.
Michael Kantar of the University of Hawaii in Manoa and his coauthors describe the state of the science in “Perennial Grain and Oilseed Crops” in the Annual Review of Plant Biology. We spoke with Kantar about the pros and cons of annuals and perennials, the progress made so far, and his recipe for experimental sunflower soup.
Why are all our grain and oilseed crops annuals?
Our major crops are all grasses, and they tend to be annuals. These grasses were easy to collect and domesticate in prehistoric times.
As farming technology progressed — using animals and then tractors to plow, things like that — we fell into this simple, annual cycle: one planting, one harvest. And being able to store the seeds of annuals means you can plant when and where you want.
What are disadvantages of annuals?
The big one is, by simplifying the ecosystem, we’ve lost ecosystem services. There are other things that we want from our landscapes besides food and fuel. We want cleaner water, we want to preserve our natural landscapes, we want wildlife habitats, we want healthy soils.
For example, areas like the upper Midwest used to be prairie, with vegetative cover year-round. Now, with an annual cropping system, half the land is bare for half the year. That creates a huge environmental problem in terms of soil erosion, with nutrients and soils being moved into water systems by rain and wind. Nitrate fertilizers flowing into the Gulf of Mexico kill fish there, to name one example.
Another is that an annual cropping system does not make a long-term place for insects and animals to use. It leaves a wide open plain with no vegetation, no food sources, no shelter sources. We need beneficial insects, like pollinators. If there aren’t areas available for these pollinators, that’s a huge problem.
How do perennials solve these issues?
You have year-round ground cover, with the roots taking up nutrients. So you’re not constantly losing your soil and nutrients and dumping them in the water. Another advantage, research shows, is that with better-established root systems, you can probably use less fertilizer, maybe less irrigation. And you’re providing a place for insects and other animals.
And it’s OK if the insects eat some of your plants?
Yes, especially if it’s the end of the crop season, that is not a problem. Perennials much more closely mimic what you would see in a natural ecosystem.
Scientists have been exploring the use of perennials for sustainable agriculture for nearly 100 years, with early efforts attributed to plant geneticist Nikolai Vavilov. The more current efforts to domesticate perennials were started by Wes Jackson and the Land Institute in Salina, Kansas, in the late ’70s. Back then, this idea of perennial crops was seen as fringe, crazy. In the last 15 years or so, it’s no longer seen as an out-there idea. It’s now seen as perhaps a challenging idea, but completely doable.
How many years would perennial crops last before one would have to replant?
There are currently a lot of ongoing studies to determine what is the optimal length of time. The perennial crops currently being explored would probably have a three-to-five-year cycle as a crop, with annual harvests.
So if we’re going toward perennials, what, in your opinion, are the best candidates to domesticate?
I think your best candidates are similar to those grains that we currently have. For example, intermediate wheatgrass is a close relative of wheat. And some of the other ones that are being worked on right now are perennial sunflowers, some perennial legumes, perennial rice.
It helps if the perennial is closely related to a species that has genetic information already available. Then you can use modern molecular biology and genomic techniques. I prefer something that has a relatively small genome, if possible. It simplifies your ability to apply all your genomic resources.
What must be done to turn these perennials into domestic crops?
We already know a lot about domestication. For example, we know to breed for plants where the seeds have no dormancy period, so if you plant it, it’ll grow immediately; and for ones that hold their seeds, so they don’t fall to the ground and get lost.
A lot of those traits, as we know from studies of domesticated annuals, are under fairly simple genetic control. So one thing we can do is to use genetic testing to identify the plants or seeds that already have the most domestic-like genes, and breed or plant those.
What about using CRISPR/Cas9 gene editing or other modern technologies to give plants the genes you want?
Oh, definitely. You have all of your genetic engineering and genome engineering technologies available. Because sequencing is so cheap, you can sequence entire seed collections, and say, Do we have the variation that we need? If so, you can use that seed. If not, then you can do something like expose the seeds to mutagens, to try to affect those specific genes. Using CRISPR technology to edit traits into a plant also is theoretically possible, but I don’t know of any projects that are doing it for the purposes of domesticating perennials.
With new genetic technology helping, how long might it take to domesticate a wild perennial?
According to the archaeological record, domestication occurred over a couple thousand years, as people moved from wild collection, to intentional planting, to selecting for plant types, until those plants became dependent on humans. Today, when people run simulations, they think it can happen in as fast as 20 to 200 years. People are making tremendous progress in how quickly these wild plants start to look like crops. Research on intermediate wheatgrass is really making quite a lot of progress, The Land Institute has varieties that produce more, larger seeds than the wild version.
What are you working on?
I am working on perennial sunflowers. We first tried to shortcut the process by crossing annuals and perennials, to give a gene for “perenniality” to the annual. That turned out not to work as well as we would have liked. The genetics were too complicated, because some kinds of sunflower have two copies of a gene, some have six, and when we crossed them we’d get plants with four copies. It became somewhat difficult to use a lot of the genomic resources that we wanted to use.
What we’ve done recently is to try a more traditional domestication approach. We’ve done a lot of DNA-sequencing projects to look for natural genes that will help us. We know in sunflower it’s important to control flowering time; you have to be able to fit it into the growing session of a region. And the oil content and quality in the seeds. So now we’re screening plants with those features to use as parents for future generations.
Have you tasted or cooked with any of these crops we’re talking about?
With our sunflower, the initial crosses we did were between the perennial Jerusalem artichoke, which is a species of sunflower, and an annual sunflower species. I tried to chop up their tubers, to make something like a potato soup, but a Jerusalem artichoke-hybrid soup. It turned out kind of slimy.
I tried again, I baked them in some butter and salt, and that was fine. What I really want to try — I haven’t, yet — is to make sunflower chips.
How would moving to perennials change a farmer’s practices?
That’s an important question. Farmers are astute businessmen; they’re very happy to switch crops as long as it’s going to provide them with profit. We have to talk to the growers, asking: What yield do you need? What’s the profit margin you need? What do you need so that you don’t need to change your farming equipment?
The goal would be to have the harvesting, planting and processing tech be very similar or the same as for annuals. The systems need to be compatible so the farmer’s investment in new equipment is not a deal-breaker.
The short answer is we’re not sure about all the effects — we’re still doing those studies. Some Australian researchers did an economic analysis. They estimated that if your perennials offer 65-100 percent of the crop yield of annuals, assuming reduced fertilizer and water scenarios, they might be as profitable as annuals.
When might we expect to see one of these perennial crops on the market?
There are many new crops that are ready to try; the question is more about the potential market and the amount of acreage that can be planted. Large-scale growth across the landscape is probably decades away, but in terms of testing and small-scale acreage, some things are ready now.
Some of these perennials are already being grown at limited scale. The Land Institute has released a trademarked line of intermediate wheatgrass called Kernza. It’s used in Long Root Ale from Patagonia Provisions. And researchers at the Land Institute and the University of Minnesota are well on their way to figuring out how to make high-quality bread out of intermediate wheatgrass.
We know how to do it; we’ve made tons of progress. It’s now a matter of, what does society value? If we make a concerted effort, we can change the landscape.