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Interview with a Plant Scientist: Stan Cox, Perennial Sorghum

Stan Cox, lead scientist for perennial sorghum, performed field research on the annual grain when he was in graduate studies. After graduation, he worked as a wheat geneticist before coming to The Land Institute (TLI) in 2000 to develop perennial sorghum. Today, with the help of Postdoctoral Fellow Pheonah Nabukalu, Stan’s research on perennial sorghum spans the globe from the U.S., where it is mainly used as a forage crop, to eastern Africa, as sorghum is an important food crop for many people in that hemisphere. In addition to his direct agricultural research, Stan has been involved with the Ecosphere Studies program since its inception and has been a featured author and presenter at the annual events.

What brought you to the Land Institute?
I worked for the U.S. Department of Agriculture in wheat genetics for 13 years, over in Manhattan. In the mid-80s when I was first there, I got to know Wes Jackson and TLI, which at that time was built around the intern program. Interns would do research, then once a year, they would come over to Manhattan and Lawrence to give presentations on their results. Because we were the official academics, we could discuss it with them, critique it, and so forth. It was called the research advisory group, and I would come out here sometimes to work with people. In the early 90s, I worked with Wes again, who was trying to get the USDA to take up the kind of work we’re doing here. We drew up a big plan, and he took it to Washington and really lobbied hard for it, but the USDA did not go for it. However, that kind of ended up being the blueprint for what he did here later.

Did you always work on sorghum? Or did you just think it was a good option for perennials?
I got my Ph.D. at Iowa State, but did the research for the dissertation in India at the International Crops Research Institute for the Semi-Arid Tropics (ICRISAT). I did all of the prelims at Iowa State, and then for two and half years, went to India and worked with their sorghum breeding program. But after I graduated, I worked on wheat. I came here (TLI) in 2000. David (Van Tassel) and I were the only two potential plant breeders at the time, so we both worked on wheat, sorghum, sunflower, and growing out other perennial species − just seeing what we had. It was also when we first brought intermediate wheatgrass [Lee won’t let me say Kernza®!!] seed in and started working with it. So, we were kind of jacks of all trades.

After Lee arrived, we divided up the crops and each had one or two that we would be the specialist in. That’s when I said I wanted sorghum (because I kind of missed it from the old days), and I had developed a terrible allergy to wheat pollen after working with it many years. So, David went into sunflower and non-grass species, and Lee worked with perennial wheat and wheatgrass. Then when Shuwen came in 2010, he took over perennial wheat, and Lee went full-time on wheatgrass.

I’ve heard that sorghum is used here (the U.S.) more as a feed crop for animals, and in other countries it’s more of a human food. Is it a different species or are people here just not in the habit of eating it?
I first want to emphasize that we are developing perennial sorghum for production of grain for human food (although the stalks, or stover as it’s called, can be used for many other purposes, including feed for cattle, goats, or sheep). Sorghum was domesticated in Africa, probably the area of South Sudan about 8,000 years ago. Strictly as a human food, it spread to India, South Asia, and China also. It remained an Eastern Hemisphere crop really until the 20th century. Then, American agriculture first brought it in as a forage crop – feeding the stems and leaves to livestock, making silage out of it, and that kind of thing. It was the 1950s when the plant breeders developed hybrid sorghum that produced good yields of grain. They aimed from the very beginning at just the livestock market − maybe because the grain was unfamiliar here − and we already had corn, wheat, oats, and other grains. But, because sorghum does well in dryer climates and is not as susceptible to drought as corn is, this part of the world from Salina west and from Texas up into Nebraska (the western parts of those states), sorghum became very popular. But those are also the areas where there are many cattle, so it became part of the livestock industry. Also, lots of it was being sent south for poultry. And then, in the past 10 years or so, it has become a major grain ethanol crop.

Because the plants are so big?
Corn was the original crop for making grain ethanol.  But sorghum, if they’re growing without irrigation and it’s dry, will produce better, and the same plant facilities that produce ethanol from maize can use sorghum. It’s continued being used as a forage crop for making silage for dairy cattle, but the main use in the rest of the world is as a grain crop. Interestingly, since NAFTA, there’s been a lot of trade between the U.S. and Mexico. Mexico grows and uses increased amounts, but strictly for livestock, because corn has thousands of years of tradition in Mexico. People aren’t going to consider eating sorghum there —until they get a taste of our food-quality perennial sorghum someday.

Do you think people will switch here? I thought I had seen something with sorghum syrup recently?
Sorghum syrup is processed kind of like sugarcane − they press the sugars out of the stalks. Those are special varieties of sorghum that have been bred to put more of their energy into stalks in the form of sugar, rather than starch into the grain. I grew up on sorghum syrup in Georgia – it was very popular in the South. It used to be that you could buy Kansas-made sorghum syrup in the stores here, but I haven’t seen it in a long time.

Do you think sorghum will have much of a U.S. market as a food crop?
It’s increasing already. Both because the national sorghum growers’ organizations have been promoting it, but also because the gluten-free market uses a lot of sorghum. It’s still overall a very small proportion of the sorghum produced but is growing rapidly. My wife Priti is from India, so we often eat sorghum chapatis. We found a place in Nebraska where they grow food-quality sorghum and mill it into flour, so we have ordered from there. There are also Indian grocery sites these days where you can order online and get shipments of sorghum flour, millet flour, and other grains. So, it may catch on beyond the gluten-free and immigrant market.

I think one thing that happened in recent years was that early, more drought-resistant forms of corn have been developed. For the past couple of decades here in Kansas, for example, corn acreage has increased, and sorghum acreage decreased. But as the water in the Ogallala Aquifer becomes scarcer and there’s less irrigation, I think sorghum’s going to make a comeback.

In terms of what’s going on with your research here – you and Pheonah Nabukalu (Postdoctoral Fellow for perennial sorghum) were working in Uganda, and you have another student from there at Texas A&M now?
The whole Uganda business kind of came about as a happy coincidence. Pheonah came here in 2013, from Uganda by way of Louisiana State University, and it just happened at about the same time that we got a grant that was specified for work there, unconnected to Pheonah. It worked out great, because we would have been operating totally in the dark if we didn’t have her! Part of that grant was to have a graduate student run experiments in Uganda, and that’s how Shakirah Nakasagga came into the picture. For a couple of years, under the guidance of Pheonah’s former professor there, Shakirah ran these studies that we just recently published on, and now in January 2018, she started work on her Ph.D. at Texas A&M. She is working with the only other U.S. sorghum breeder who is interested in this point in perennial sorghum.

While that was happening, our colleagues in Sweden (they’re social scientists), got a grant to work with farmers with perennial crops, again specifically in Uganda. So, when Pheonah and I were there in January of this year, it was in connection with that study, because we supplied the seed and are consulting with them on that.

This diploid discovery – could you explain a little about that? It looks like maybe it will make it easier to work with some of your different research partners in crossing plants?
That’s a good part of it. It’s not an easy thing to explain why it’s so worth doing, but sort of the general bottom line is that because our source of perenniality is a 40-chromosome sorghum, all our gene pools that we’re working with are 40-chromosome material, and there are various disadvantages. One of them is that there’s the worldwide sorghum gene pool, and then there’s our gene pool. If we want to use whatever useful material we can get out of that whole gene pool, it’s not easy to get it from the 20-chromosome (diploid) gene pool into the 40-chromosome (tetraploid) one. We are always looking for ways to be able to broaden the diversity that we can take advantage of.

Then, these 40-chromosome plants have various problems of their own. They don’t produce pollen as well as 20-chromosome plants, and because they have four copies of every gene instead of two, it’s hard to stabilize a certain trait if you select a plant that has exactly the traits that you want and grow out its offspring. Some of them may have it, but most don’t, so it takes many generations to what you call “fix the right genes” in plants. So, this discovery that we can extract populations on a large scale from the 20-chromosome gene pool and use them as 20-chromosome plants will, I hope, be a help to us.

Is it that the more genes there are, the more possible permutations there are of things?
That’s basically it. For example: There are four different places in the sorghum genome where there’s a gene that governs the height of the plant, and in general, when we cross with the wild species, we get these huge, tall plants. We want to get them shorter. The gene for tall plants is dominant, and so that means if you have a diploid and it’s a hybrid (so it has one tall gene and one short gene), and then you self-pollinate it, you get three tall plants and one short plant. And then you self-pollinate more, you get down to about 50/50 – about half tall and half short. But if you have four copies (say you have two tall genes and two short genes in there), then it takes much longer to identify short plants. So, the next generation, it may be that one out of 16 plants is short. But, say you need two of those short genes to be fixed, then it’s one plant out of 256, and if you need three, then it’s one plant out of 1,000.

Is that the most important thing that you’ve found recently, or have you had any other new discoveries that you would consider as important?
It’s potentially a big deal. What we don’t know yet (we haven’t had a chance to do enough testing), is if we can get 20-chromosome plants that are perennial. Or when we lose half the chromosomes, is it harder to get a perennial plant? If we can, then it will be a big breakthrough, but we’re waiting to see.

The other encouraging development in the past couple of years is that we’re getting more perennial plants that have individual seeds which are closer in size to grain sorghum. In general, for a food crop, large seeds are better, however it’s not absolutely necessary. Millet for example, and teff, which they eat in Ethiopia, have very small seed, but generally, it’s easier to mill, process, and so forth with a larger seed. So, after years of trying to select for both perenniality and large seed in the same plant, and having a hard time doing it – after many cycles of crossing back to grain sorghum, we’re getting some larger seed.

What would you say are your goals for the next five to ten years?
I think that the more near-term potential, based on our experience in Uganda, would be for growth in the tropical environment with subsistence farmers, because there are a lot of other requirements if you’re going to have large-scale mechanized agriculture that are going to take more time (to develop). Also, because in a place like Kansas, the plant not only has to be perennial, but must be able to survive very low temperatures. That’s just one more obstacle. We know if we see a plant here that has the traits needed for perenniality, in the tropics, it will definitely be perennial. Here, it may or may not, as they often can’t survive the cold. So, I think in warm climates and where mechanization is not such a big deal, we may have something in that 10-year time frame.

Are you going to be involved with teaching the July 2018 Ecosphere Studies workshop?
Yes, it will be the third or fourth year that we’ve had people come in the summer, and I should be doing a presentation or involved somehow. However, I always learn more than I impart!

In addition to his scientific publications, Stan has published four books:

Sick Planet: Corporate Food and Medicine (Pluto Press, 2008)

Losing Our Cool: Uncomfortable Truths About Our Air-Conditioned World (And Finding New Ways to Get Through the Summer) (The New Press, 2010)

Any Way You Slice It: The Past, Present, and Future of Rationing (The New Press, 2013)

Stan Cox and Paul Cox, How the World Breaks: Life in Catastrophe’s Path, From the Caribbean to Siberia (The New Press, 2016)

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