What Your Corn Eats

Walter Goldstein of the Mandaamin Institute discusses how corn bred for optimal microbial interaction — varieties that utilize the rhizophagy cycle — can supply its own nitrogen and other nutrients and can outcompete weeds 

Acres U.S.A. Could you tell us some of your background and how you got into corn breeding?

Goldstein. Sure. I have my master’s degree and doctorate in agronomy from Washington State University with a major in production and minor in breeding. And then I spent 25 years at the Michael Fields Agricultural Institute as a research director. In 2011 I started the Mandaamin Institute to continue the breeding work that we had been doing.

Acres U.S.A. What were your original crosses? And what were your original goals, and have those changed over the years?

Goldstein. Yes, they have, to a certain extent, but not in depth. When I first got started — this was in about 1987 — I was at a field day surrounded by a bunch of older farmers who were sustainable, or organic, or regeneratively oriented. They told me that they wanted me to work on breeding open-pollinated corn because they knew that it had better nutritional value and that animals liked it better than conventional corn. But they couldn’t grow it well because it would fall over at normal plant densities. They didn’t want to grow it on a larger scale because it hadn’t been bred for high population densities. But they knew it had better protein content and more minerals, and they wanted somebody to work on it. 

So, they asked me to do that, and I didn’t quite know what to say. I had been involved in some selection work while I was at Washington State, and I was interested in corn, but I didn’t have much experience with it. The next summer I visited a gentleman named Albert Arens who was a kind of a maverick breeder in northeastern Nebraska. He had a company called Green Acres in Hartington, and he would breed for a lot of the organic farmers. He bred corn without any fertilizer. 

I went to visit him and had a long conversation with him just before he died, and his nephew sent me a bag of corn that he had developed for planting at low plant populations in the dryland farming areas of Nebraska. It could respond if it was really dry, but if it was really wet and had lower densities, it would produce a lot of ears on each plant. I started experimenting with it and making crosses with native corn, because I was convinced that the native corn had the quality we’d lost with conventional breeding, and it needed to be bred back in. 

I did that for about 14 years — breeding open-pollinated corn for farmers. I had a small clientele of farmers who were interested in it, and I’d go and select on some of their farms with them every year, but it was a small group of people. 

Then we got to the turn of the century, and GMOs came in, and the organic farmers were very upset because they knew that their corn was going to get contaminated and they were going to be holding the bag.

So we had three listening sessions at organic conferences in Iowa, Wisconsin, and Minnesota. By that time I was working together with USDA and doing some projects with them, and we managed to get an appropriation to breed for organic farmers. We asked the farmers what they wanted. We knew what they didn’t want — they didn’t want GMO corn. 

It turned out that there were three things that they were interested in. One was crops that would do well without nitrogen fertilizer. They wanted to use their own organic matter — the nitrogen sources from their farm — to grow their corn. The second one was weed control — they wanted corn that would compete well with weeds. And the third thing was nutritional value, although there was a bit of a split with this. The farmers who were just growing to sell grain didn’t want to take any yield loss for quality, because they weren’t going to be paid for that. But the farmers who were raising their own animals were more interested in it. 

We got the same answers in the three different sessions. The majority of the farmers wouldn’t accept anything more than a 10 percent yield loss, even if there was higher quality. They didn’t want open pollinated because they knew it couldn’t yield that high. They wanted hybrids. 

So, we made a strategic decision. While there were a few farmers who wanted open pollinated so they could keep their own seed, and we liked working with them, the vast majority of those farmers, whether they were organic or just inclined in a sort of regenerative way, didn’t want to lose much yield. 

After we got the appropriation from USDA, we worked with them for a while. We had a nursery and trials in Wisconsin and Iowa, and we developed an organic nursery in Puerto Rico — the first winter organic nursery on the planet, as far as I knew. 

I was very interested in this whole issue of weed competition and the microbes we had found in the plants. We found that inbreds that were developed under conventionally farmed conditions generally did pretty poorly under organic conditions unless you fertilized them heavily, but they would tend to adapt to organic conditions even though they were genetically pretty fixed. That was something strange — they’re not supposed to do that from the standpoint of conventional thinking about the genetic fixation that comes with developing an inbred. But something was happening in the plants. They were shifting and becoming more nitrogen efficient. 

The study that we published in Open Agriculture showed that over time, inbred plants that were developed under conventional conditions became more nitrogen efficient when grown repeatedly under organic conditions. So, we were wondering, “Are the plants accumulating microbes — or developing partnerships with microbes — that help them to get to nitrogen, even though they’re supposed to be genetically fixed?” 

We also saw that the plants were becoming more plastic — that they were able to adapt to our conditions. Longer-season varieties from Iowa, grown organically in southern Wisconsin, became both earlier maturing and more nitrogen efficient. The plants were adapting to our conditions, but they were supposed to be genetically fixed — so what was going on here? 

That eventually led us to do some experiments. We had discovered that our corn grain was very high in the essential amino acids methionine and lysine. Those are really important for everybody who eats corn because they’re the essential amino acids that are generally somewhat lacking in normal food and feed. Organic chickens are often fed synthetic methionine, but we had enough methionine in our corn that the farmers didn’t need to supplement it to their chickens. We did studies with Organic Valley on that — with broilers and with layers — and discovered there was no bonus for feeding synthetic methionine if we fed our corn, because it was so high in this. We also discovered that our corn was very high in minerals — much higher than conventional corn. 

We began to think, “Maybe microbial partnerships are evolving in our plants. They’re responsible for increasing the methionine and the minerals because maybe they’re part of this whole picture. Maybe that’s why we have much better nutritional value.” The high-methionine corn came two different ways — in hard-kernel corn and soft-kernel corn. The hard-kernel corn had a high methionine content because it was really high in protein, and methionine is part of protein. 

But the poultry people didn’t want that. They didn’t want to have super high-protein corn. They wanted to have fairly normal protein, just with a lot of methionine in it — and we had that with our softer-kernel corn. And we had some hard-kernel ones that were like that too. But we started doing experiments with the hard-kernel corn, because we that found that from farm to farm, it was really hard to get a reliable protein content in the corn. Sometimes it’d be low, sometimes it’d be high.

We started inoculating with nitrogen-fixing bacteria to see if we could make the protein content more stable. That was especially important for the hard-kernel, high-methionine corn. We did an experiment in 2009 at Michael Fields, when I was still working there, on their farm, and we inoculated with bacteria on a site that was really limited in its nitrogen-supplying ability. We had identified some landraces — these ancient corn varieties from Central America and South America — that we thought had really good nutritional value. We grew them next to our breeding families and breeding lines and inbreds and a whole bunch of conventional varieties on a nitrogen-limited soil. 

Everything was pretty deficient in nitrogen except for those old landraces. The conventional inbreds were the most deficient. Our breeding families were not so bad — they were in between — but some of the old landraces looked like they’d been heavily fertilized with nitrogen fertilizer. We did some natural abundance isotope work, and it looked as if some of them had been fixing up to half their nitrogen. We made crosses between those landraces and our corn, and with conventional corn too — older inbreds from Holdens Seed Company and Pioneer and so on — and we started breeding with it. That led us into this whole issue of trying to pursue a nitrogen-efficient corn that’s partnering with bacteria in order to get its nitrogen. 

After I published on this with some of my colleagues, I got a letter from James White from Rutgers University, and he said, “I think I know what’s going on with your corn — how it’s getting the nitrogen.” We had a good conversation about this and about rhizophagy. He thought that our corn was utilizing the rhizophagy cycle. He had done experiments with another corn breeder who had been breeding white corn, but he couldn’t find any evidence of rhizophagy in that white corn — but he could find it in ancient landraces. 

So, we sent him our corn, and I came over to Rutgers and saw with my own eyes that there were gangs of bacteria inside our little seedlings. He germinated them on agar after surface-sterilizing the seed, and there were just so many bacteria inside our plants. I also sent him inbreds that we had grown side by side with conventional inbreds, and in the conventional ones you just couldn’t see the bacteria. But with ours, they were crowded and they were popping out of root hairs and getting out of the plant to colonize the outside of that rooting system as fast as possible. 

That really got us excited. We started working together, and he started exploring what was going on, and we got ourselves a good microscope. James and I and another microbiologist got a grant to work on these partnerships, and we’re going at it pretty strong. James has been teaching us how to do good microscopy with these endophytes.

We’ve discovered that some of the corn varieties we’ve developed are really superstars — they have these microbes. Some of them are extremely dark green. They’re darker green than conventional corn, even when they grow in very nitrogen-limited sites. They often have somewhere between 15 percent and a third more chlorophyll in the leaves just before anthesis — before flowering. So, they’re getting that protein — they’re getting that nitrogen — and they’re making a lot of chlorophyll. 

And we discovered that the plants are simply loaded with bacteria. Apparently they’re in the embryo. They’re in the growing apices of the roots and the shoots. They’re colonizing; they associate with the nuclear membrane, and they seem to be released from the nuclear membrane of the cells. Every cell has a nucleus, and there’s a sort of skin on the outside of the nucleus, and the bacteria seem to be harbored there. They seem to go in and out of that skin. We see them being released out of vesicles, which are secreted out of these nuclei. 

We see these microbes in the germinating seedlings especially in the root cap cells that are excreted. The root tip, as it pushes its way through the soil, populates the area around the root with its own cells, which are full of mucus. They produce this sort of slime, which the root can slip along through. And in our plants, they’re just absolutely crowded with different kinds of bacteria in there. You can see them — they’re different sizes and shapes, and they’re often in these muco-producing organelles inside the cells.

These are polysaccharide substances that are produced by the plant, and they stick the soil to the root, and they create food havens for bacteria to do things in places that are low in oxygen. They could be good sites for fixing nitrogen. And also, of course, bacteria thrive on that stuff. And so you have this area where there’s a tremendous amount of bacterial growth, and in our plants these interfaces are accentuated between the roots and the corn.

Acres U.S.A. That’s all such fascinating stuff. You mentioned that the bacteria are particularly in the apical cells — in the meristem, both roots and shoots. Are they in the normal leaf cells as well? 

Goldstein. They are. I have a picture of a seedling at the two-leaf stage, and you can see that the chloroplasts are colonized by these bacteria already. They’re there right from the get-go, and they colonize the chloroplasts. They’re sitting there where the plants are producing sugars. The research from the ’60s and ’70s indicates that in the presence of bacteria, plants produce more chlorophyll.

I think what’s happening is that the bacteria are stimulating chlorophyll production, and they’re living there, and they’re probably living off of the sugars. We could speculate whether or not they’re fixing nitrogen because there’s probably a need for it in order to make that chlorophyll — all these photosynthetic proteins are the bulk of the protein in the growing plant, and that means that they’re the bulk of the nitrogen sink. That’s where the nitrogen goes, and they need a lot of nitrogen. So it is kind of a convenient partnership right there. 

But we also see a lot of colonization in trichomes, which are these hairs on the plants. Bacteria aren’t just in the root hairs. Our plants have lots of long hairs, and there’s bacteria inside those hairs. We have a video on our website of bacteria rotating around like crazy in those trichomes. They’ll do that in root hairs too. It may be that that’s a site for multiplication of bacteria in that culture inside those trichomes. 

The trichomes are anchored in the skin of the plant, in the epidermis, and right below it are all these convoluted cells where these bacteria seem to migrate to, and they seem to die there. We have another video on our site of an epidermal leaf area where the cells are beginning to form these heavy walls. I think it’s a gradual process of forming these walls. They’re almost like prison camps where the bacteria seem to be going and dying. 

I’m also thinking that there’s a lot of absorption of nutrients in this way. I think these plants are cultivating bacteria in this soil. They’re taking them up behind the zone of exudation, and they’re entering into the body of the plant. They’re being attacked by reactive oxidative substances that the plant produces — superoxide and hydrogen peroxide — and the plant is eating the cell walls off of these bacteria and then excreting them out of the root hairs — or they’re leaving out of the root hairs and forming the walls again when they get on the other side of the root, in the soil. 

That’s why we’re getting so many minerals in our breeds of corn, but we’re also getting more nitrogen because we’re getting a lot of nitrogen from these bacterial bodies. The plants are actually consuming these bacteria. And we saw that when we did our isotope studies. To our surprise, the plants were concentrating ¹⁵N in their leaves and stalks and roots. The ¹⁵N:¹⁴N ratio was skewed in favor of the heavier isotope of nitrogen. There are two isotopes of nitrogen that are naturally occurring — ¹⁴N, which is most of the nitrogen, and ¹⁵N — and it seems that bacteria accumulate ¹⁵N in their bodies. So do all animals — we seem to like the ¹⁵N better and get rid of the ¹⁴N. Our plants have higher levels of this ¹⁵N in their bodies, and we’re assuming they’re getting it from actually consuming bacteria. 

The other line of evidence supports the idea that the bacteria are dissolving in the plant and being assimilated by it. We have been working with Willie Pretorius from Ward Labs to measure the fatty acids in the plants and to analyze them for their composition. And the fatty acids are different according to where they came from. Fatty acids from cell walls of bacteria have different lengths and different branching patterns than ones coming from fungi. Willie has been able to help us to distinguish what kind of bacterial cell wall fatty acids and fungal fatty acids we have in our plants. 

When we looked at our inbreds, versus inbreds from Pioneer or Monsanto, it looks like we’re accumulating a lot more fatty acids from bacteria, particularly gram-negative bacteria, and also from mycorrhiza. This is support for the observation that the plants are consuming these bacteria. The plants are assimilating bacterial bodies. It’s kind of like the plant is a bioreactor.

Acres U.S.A. That’s incredible. What happens if you take your varieties, which are bred to assimilate with all these different microbes, and put them in a conventional soil, which for all intents and purposes is dead bacterially and fungally? And conversely, what if you take a conventionally bred seed and put it in a living soil? It probably isn’t even going to know what to do — it’s used to getting its nutrients basically hydroponically.

Goldstein. Right. It’s used to getting mineral fertilizers out of the water. And the rooting systems show that — our rooting systems are densely branched in the top soil, and the conventional ones are very vertical. They go straight down looking for the water with fertilizer in it. These differences are clearest if you compare inbreds with hybrids; it’s complicated, but between inbreds, you can really see the difference on nitrogen-limited soils. 

As for putting our varieties in a conventional soil that’s microbially deficient, that’s a good question. We don’t have much information on that. We had a SARE grant and did research with a bunch of farmers — a couple conventional, but mostly organic — and we saw that there was a positive relationship between the amount of soil protein and the performance of these plants. Soil protein is a proxy for microbial biomass. I think that our plants, if they’re forming a lot of their bodies out of microbial bodies, are going to do better in a soil that has more microbial bodies in it. 

But even on poor soils, we have seen that our corn, without any fertilizer, often outperforms the conventional ones. I suspect that our plants are putting more of their efforts into growing roots and feeding microbes, and that pays off under stressful conditions, and it pays off under conditions where the nitrogen supply isn’t great. But if you have a corn that’s developed to be a kind of racehorse under high-nutrient, racehorse conditions, with everything oriented to getting maximum yields, you’re comparing a racehorse with a workhorse. Our corn is stress resistant and good at growing under conditions where fertility levels aren’t excessive, but it does do well. It just loves good organic matter and microbial biomass.

Acres U.S.A. Could you also talk about your other original goal of plants that are able to compete well with weeds?

Goldstein. Sure. We’ve met that goal. Our inbreds are very vigorous. They’re not super uniform, but they’re very vigorous. Part of not being uniform is that we’ve been selecting for plants that are very vital and have less inbreeding depression. They’re kind of mavericks, in a way. They’re more mobile, and they’re more “plastic” in their relationship with their genome — they can move things around, they throw out new variations, etc. 

And because we were always selecting for plants that could compete with weeds, we couldn’t breed inbreds that were short. We need to have inbreds that are strong and robust. I think the people who produce organic hybrids appreciate inbreds that are tall and strong and can compete with the weeds. There are certain ones that are more competitive than others. We’ve been studying this last year — we had a study where we had a very weedy site, and we saw that hybrids with certain parents seemed to even inhibit weeds. There were fewer weeds in the row with certain parents than others. 

And then we have the LAT-7 breeding family, which seems to be very good at competing with weeds. We rented a piece of ground that had been in alfalfa, and nobody knew that there were thistles underneath it like crazy. When we started growing it, it all came up and was just a thistle bed. At the end of the year, when we got our yields, we had an awful lot of hybrids that yielded between 60 and 80 bushel, but we also had certain hybrids that were yielding up to 160. And those ones all had LAT-7 in them, which is a very nitrogen-efficient corn that was bred with Mexican corn that is reputed to fix nitrogen. 

So, we have certain groups of corn that seem to be the ones that are the most nitrogen efficient, that seem to be better at controlling weeds, and we think that they dominate the soil. It could be that they’re exuding microbes that have negative effects on weeds. We think that happens. James White is really into that — “interbiome interference” he calls it — where bacteria are excreted from one plant to another and the bacteria actually inhibit competitors for that plant. They’re like servants for the particular plant. There’s lots of that going on under the ground. It could be that our plants are doing some of that. 

We suspect that is the case particularly with an inbred family called C4-6 — that it’s inhibiting plants that grow around it. But on the other hand, we’ve been doing studies growing C4-6 and beans together. If we can combine the two together — and we think we can for silage — it could be a very good cropping practice. That’s Phaseolus vulgaris — that’s a climbing bean, not a bush bean. It seems as if beans grown together with C4-6 do better than when they are grown with other corn varieties. We’re working with some Germans on this who are interested in growing corn and beans together for silage to reduce the use of nitrogen fertilizer. 

Acres U.S.A. What kind of spacing is that? Is that with wide-row corn?

Goldstein. No, they’re planting narrow row, with the two plants of corn and one of beans, and they have bred beans that are low in a toxin called phytohaemagglutinin so that it won’t be a problem for the cows to eat the two together. These are special beans. 

Acres U.S.A. What about gametophytic incompatibility — breeding seed that can only be pollinated by its own variety — is that something you’ve been able to put into any of these open-pollinated breeds? 

Goldstein. Yes, we’ve been working on that for many years. The problem was that we couldn’t get the yield, but last year we did. We keep on trying different things and refining what we have. 

Acres U.S.A. How does that work? Would it exclude all genetically modified pollen?

Goldstein. If it’s working well, it should take care of most of the pollen. Maybe not a hundred percent; it could be 99, 95 percent. So it helps to reduce contamination. It’s a barrier. You find it in teosinte, the wild corn. It keeps itself from being pollinated by normal corn.

Acres U.S.A. Have any of the big companies tried to take that trait and put it into their own seeds with genetic modification?

Goldstein. There was certainly a worry about that, but to my knowledge, it hasn’t happened yet. That’s a long story. It’s been very contentious, and there’s been quite a bit of tension between different people about it. 

We are working on this cross incompatibility and trying to combine it with nitrogen efficiency and nutritional value. We were pretty encouraged last year, and this year we’ve got a bunch more trials out, and we’d like to advance something.

Acres U.S.A. On the more practical level, are you planning on selling seeds yourself through the Mandaamin Institute site?

Goldstein. Our hybrids are presently sold through Foundation Direct Seed in Onalaska, Wisconsin. We’re also planning on a subscription model out of the Institute itself. We have a number of people producing hybrid seed for us, and I think they’re going to be selling seed. And we have one Amish farmer who sells an open-pollinated variety for us. We’d like to start a subscription program to get people involved in doing their own breeding — learning how to breed and take care of their seed. 

It’s kind of like guerilla warfare! The way the system is currently set up is all based on patents and just trying to make money. As a small organization, it’s really hard to advance what we do within the framework of the conventional system. We have to be inventive and try to figure out different ways of getting this corn out to farmers. 

We view it as a responsibility. We’ve discovered how absolutely incredible it is — what’s going on inside these plants — and we need it now. Humanity needs it; the planet needs it. We’ve got to stop using all this nitrogen. There are no good solutions except maybe this one. 

Learn more about the work of the Mandaamin Institute mandaamin.org.