Wisconsin Public Television University Place  Carrots and Vitamin A  Philipp Simon  7/31/13 UP902  cc >> Welcome everyone to Wednesday Nite at the Lab. I'm Tom Zinnen. I work here at UW-Madison at the Biotech Center. I also work for UW Extension-Cooperative Extension. On behalf of those folks and other organizers, Wisconsin Public Television, Wisconsin Alumni Association and the UW-Madison Science Alliance, thank for coming to Wednesday Nite at the Lab. We do this every Wednesday night, 50 times a year. It's another way that you can share in the discovery from research at your public land grant research university. Tonight it's my pleasure to be able to introduce to you Phil Simon. He's a carrot breeder here at the Department of Horticulture, and also with the Agricultural Research Service of the US Department of Agriculture. He grew up in Carlsville which is in Door County. 

He got his undergraduate degree at Carroll College, now Carroll University. Then he did his PhD work here at UW-Madison in genetics. He's been on the faculty here since 1979. One of the great things about his story is that he's going to continue to share how vitamin A research has played out in the last century and into the coming decade. We're continuing our commemoration of the centennial of the discovery of vitamin A here at UW-Madison back in July of 1913, at least that's when the paper was published, by Elmer McCollum and Marguerite Davis. This is the fourth in our series of talks on vitamin A. It's a really good example of how investments and discoveries made a 100 years ago continue to thrive as research topics of pretty vital importance to us here in Wisconsin and to people throughout the world. Tonight we get to here about the role of plant breeders and plant breeding, and making carrots an even better source of vitamin A. Please join me in welcoming Phil Simon to Wednesday Nite at the Lab. [applause]  >> Thank you, Tom. 

I really appreciate the introduction. I very much appreciate the opportunity to speak to you tonight about some of the research I'm involved it. As Tom mentioned, I'm in the horticulture department. I'm a USCA researcher and also a faculty member here. I'll be talking primarily about carrots and vitamin A, but I'm going to introduce the topic a little more generally talking about, really, food and people. There's a very interesting interaction that really has taken place over the millennia that's a relationship between us humans and plants. I'm going to talk about that in the particular case of the relationship between vitamin A and humans. But let me introduce the topic by talking about plants and people a little bit. Really the history of the development of agriculture is a very interesting one. I think that we can better understand this close relationship we have with crop lands if we look at the process of domestication and the interaction that we've had with croplands as they've been developed for modern use. 

There was a time, not that long ago really, probably 10,000 or 15,000 years ago, where people lived off the land strictly by hunting and gathering. They were initially raising herds, and moving them around and feeding them on the crops that were just growing wild in the countryside. Around 10,000 or 12,000 years ago the first civilizations developed, initially in the fertile crescent. In this region of the fertile crescent-- Oops, excuse me. I've got to go back. Let's see here. In this region of the fertile crescent there are some major developments that reflect the interact of humans and plants, and in this case, humans and animals as well. In the fertile crescent wheat and barley were domesticated. Also in this region sheep were domesticated. The map in the upper right-hand corner shows you this part of the world in that region from the Mediterranean Sea in a crescent shape, through Turkey and into Iraq and Iran. 

It was this first agriculture that was very important for the development of human civilizations. Not too much more recently than this, in other parts of the world, other crops and animals were domesticated, in northern China, Peru and Mexico. These crops were domesticated, from what we can tell, because of the fact that there was ample water and there were plants that could be domesticated in these regions at that time. This domestication process is an interesting one. I think that Jacob Bronowski captured, really, the results of domestication the best in this short phrase. He said, "Humans domesticated crops. Then crops domesticated humans." The upshot of this statement is that crops, in their domestication, have allowed us to really develop into the human civilizations that we have today. It was these domestication processes that allowed people to live in one place, to live off of the land without moving around, without moving their herds, and to really take the time to develop civilizations. That really hadn't been possible before this whole domestication process. It was because of the crops that were initially wild and then domesticated in these regions that really provide the basis for the development of human civilization. 

The first major crops that were domesticated that we're familiar with are staple crops. These are domesticated because they provide a source of nutrients. Nutrients for us as humans, but also nutrients for those farm animals that we were domesticating along the way. We see here some examples of what happens to crops in the process of domestication. To your right there's a couple of photos. The upper one is wild wheat, the predecessor to domesticated wheat. Not too long after domestication, some preserved early domesticated wheat. You can see that in the process of domestication. The wheat kernel was enlarged by the process of early plant breeders selecting for larger wheat kernels. We don't have written records, but it's evident from this kind of record, that crop domestication in the case of wheat, enlarged the kernels of wheat. 

Similarly for corn, on the left side of the screen you see up here. You see the size of corn cobs starting about 7,000 years ago up to modern age. And somewhat comparable to wheat, you see the corn cob, and at the same time the corn kernel, was enlarging. Again, these were becoming major sources of food. The larger the crop that could be grown and sown, the more people that could be fed. We're quite familiar with these  processes of domestication, initially with the staple crops. I mentioned corn and wheat. Corn from the Americas, wheat from the fertile crescent, crops like rice in Asia and potatoes in South America. These became what we today know as staple crops. They were so important for the early human civilizations because they were sources of calories for people that were starting to develop villages, and then cities. 

They really set the groundwork to the civilizations that we know. And also to feed the animals that were being domesticated along the way. In addition to these staple crops we humans have domesticated quite a few other crops that include things like fruits and vegetables. Whereas staple crops primarily were domesticated as a source of calories, and I think some of you may have heard Dr.Tanumihardjo talking about crops like corn also being sources of vitamins. Staple crops can be sources and are sources of some vitamins in the human diet, but fruits and vegetables are really a primary source of vitamins in the human diet. It's with these domesticated versions of fruits and vegetables that we fulfill some of our nutritional requirements today. The history of our understanding of essential vitamins and food needs beyond the obvious problems that come with too low of a caloric intake, starvation, but the more subtle deficiencies. Something like vitamin C deficiency wasn't really observed very well until the 1700's in the form of scurvy when there was some association between the consumption of citrus and the reduction of the symptoms of scurvy. Even something like scurvy wasn't well understood until the 20th century, that is was in fact vitamin C in the citrus that was alleviating those symptoms of scurvy. In fact, the very first clear definition of a chemical basis for a reduction of a nutritional deficiency happened right here across Henry Mall in the building marked Agricultural Chemistry with the discovery of vitamin A in 1913. 

Oops. Let's see. In 1913, E. V. McCollum, pictured on the left here, is accredited, with Davis, to have discovered vitamin A. I'll talk a little bit about McCollum's experiments. I'm also going to talk about Harry Steenbock because, those of you familiar with the University of Wisconsin campus, are very familiar with Steenbock library and other remembrances of Steenbock. Steenbock was, to some extent, involved in vitamin A research as well. He was the individual that did some of the first work to demonstrate that there's vitamin A activity coming from some of the pigments that occur in plants. This work was published initially in 1918, 1919. I'll mention along the way also that McCollum and Steenbock are also credited with discovering vitamin D. Very briefly, to give you some background on the vitamin A research that McCollum did, because it really set the groundwork then that Steenbock did, and that we're really basing our work on carrots from today. 

What McCollum did, coming from Yale having done his PhD there, he arrived in Madison in 1907 in agricultural chemistry. If you go across Henry Mall, above the door, you see the word 'biochemistry' in paint. Above that you see 'agricultural chemistry' in stone. McCollum came to that department and discovered, among other things while he was here for about a decade, that a fat-soluble extract of butter or of egg yolk supported healthy growth of rats. In fact, McCollum was one of the first scientists to use rats as a model organism for nutritional research. People today are familiar with rats in science, and a lot of it started with work like what McCollum was doing. He was looking at the question of what is it in food that supplies essential nutrients to us. It was these essential nutrients in butter and egg yolk, but not in lard or olive oil, that McCollum noticed provided a source of a supplement to a rat food diet to support healthy growth of rats. In 1913 he called this-- Not in this paper but in a book that he wrote, he called this fat-soluble A. It got to be known as vitamin A. 

Not all that long after his discovery of vitamin A McCollum left Wisconsin and spent a number of decades finishing off his career at Johns Hopkins. In the wake of his research, in fact at the same time McCollum was here, Steenbock was here, as a graduate student initially, and then as a professor. Steenbock finished his PhD also in agricultural chemistry, or biochemistry, in 1916. He had spent a year at Yale and also a year at the University of Berlin. In 1920 he began his faculty position here at Wisconsin, up through 1956. I put '56+ because there was a required age of 70 retirement in that era, and the Regents really allowed Steenbock to continue beyond age 70 even though, by law I guess in that era, the mandatory 70 retirement came along. Steenbock was a very well known and famous professor earlier in his career, and became more famous as he went along. I'm not going to say too much about the wide range of things that Steenbock was involved in. I'm mainly going to talk about the work that he did that was more related to vitamin A. But leave it as simply that Steenbock had a fantastic career here and did so many things, including both research and, really, the development of the Wisconsin Alumni Research Foundation. 

What I mainly want to talk about for Steenbock's work that really has a very immediate connection with the work that we're doing with carrots yet today. That is his discovery in 1918, 1919 that there's a comparable type of health benefit from consuming, in Steenbock's work, carrots that are similar to the health benefits that McCollum had observed a few years ago in feeding rats with the extract of butter and the extract of egg yolks.  I'll say a little more about Steenbock's work. He didn't only look at carrots, but also sweet potatoes, parsnips and a number of other crops. And he also did some follow-up work using maize as an experimental organism. Later on he and McCollum co-discovered vitamin D. A little bit more about the details of Steenbock's work, which again, comes on the heels of McCollum's discovery of vitamin A. Steenbock recorded some similar functionality of a plant extract-- Excuse me, of dried plants in this case, starting with dried carrots and some other plants. And in plant extracts similar to what the vitamin A activity that McCollum had observed less than a decade earlier. In the case of Steenbock's work, he did some similar feeding trials that McCollum had done. 

Steenbock's work looked at supplementing this rat diet which otherwise provided calories and some minerals, but it was otherwise very much without what we know today as vitamins. He supplemented the rat diet between zero and 60% of a range of dried plant products, including carrots. The big part of the publication is on carrots. With as low as 15% of that rat rat diet being dried carrots, normal rat growth was sustained, including the ability of the females to bare healthy pups and to rear them. This was initially first a short publication in Science, 1918, and then followed up in 1919 in the Journal of Biological Chemistry. Steenbock did work with a number of different plants. He found a similar health enhancing effect by using dried sweet potatoes in this rat diet. At a little percentage than carrots, 25% of the diet, that also enhanced rat growth as 15% carrots had enhanced. In contrast to the supplements of at least 15% carrots or 25% sweet potatoes Steenbock used a fat-soluble extract of carrots and got the same positive health enhancing effects. But when Steenbock supplemented the diet of these rats, different rats actually, with 15% dried rutabaga diet, or more than 15%, normal growth of rats was not observed. 

In fact, the rats really died a miserable death of nutritional disease as a consequence of this diet. Steenbock looked at quite a range of plants. I was interested to see taro. I wasn't aware there was much taro available in the early 1900's in this part of the US. Steenbock used dried taro, red beet, parsnip, sugar beet, potatoes and mangels. I'll show you some pictures of mangels if you're not familiar with them. He used these to supplement the rat diets and found no positive effect in terms of enhancing the health to a normal type of growth in rats where their diets were supplemented with these other plant extract, or dried plant products. They gave similar lack of effect as rutabaga. In follow-up research Steenbock did very parallel research but rather than using a range of different dried plants he used only one plant, but eight different varieties, in this case, of corn, four white kerneled corns and hour yellow kerneled corns. Just, again, to show you what-- I think you all know what carrots and corn look like. 

I don't know if you're familiar with white corn. White corn was actually quite a bit more popular earlier in the 1900's than it is now. In part, yellow corn became popular because of the orange pigments in it that enhance animal growth. Steenbock's major crops he used in this 1918, 1919 work were carrots, rutabaga-- I couldn't find an on-line picture of a cut open rutabaga. Rutabagas are purple on the outside, but they're generally white or very pale yellow on the inside. Then this major study with yellow and white corn. The other crops that Steenbock used that did not allow for normal growth in rats were potatoes, parsnips, taro, sugar beets, beets, and mangels. One thing in common with all these crops that did not enhance and lead to normal type of growth was the lack of these orange pigments that occur in carrots and sweet potatoes. Red beets do have pigments, but it's a different class of pigments. You can see a picture of mangels there. 

These are the crops that Steenbock used in his studies and I wanted to-- Because I work on carrots, I was particularly interested in what Steenbock had to say about carrots in this 1919 paper. He said, "Carrots are remarkably rich in the fat-soluble vitamine." That's the way vitamin was spelled until about 1925. And, "On as low as 15% of carrots as the sole source of the fat-soluble vitamine, female rats are able to raise their young without any indications of a deficiency." He even went on to say that his observations on carrots perhaps served as a justification for the use of carrot juice as an adjuvant to the diet of children. Steenbock was impressed by the results because they really gave a normal growth and life pattern to rats. These were the first indications that there was something similar in carrots and sweet potatoes that had the same type of effects in terms of promoting normal rat growth that McCollum had observed with the extracts that became known as Vitamin A in his butter and his egg yolk work less than a decade before Steenbock's work. So what was in carrots and sweet potatoes that accounted for these effects that were similar to McCollum's? I should say that in Steenbock's papers he draws many comparisons to McCollum's work. Of course, he knew McCollum and know that work. He saw such a very similar pattern from feeding carrots and sweet potatoes that McCollum had seen that he was really very much tying the two together. But he didn't have a good idea of what it was in carrots and sweet potatoes that might account for this. In fact, it wasn't until 1930 that a British researcher, Thomas Moore, demonstrated that in fact, it's these orange pigments that are in carrots and sweet potatoes that account for the vitamin A activity that Steenbock had observed. 

When a beta-carotene molecule is cleaved in half, as it is when we eat carrots or sweet potatoes, each half of that beta-carotene molecule gets hydroxylated and becomes a retinal or vitamin A molecule. In fact, when you and I eat carrots or sweet potatoes-- Or when cows eat grass, there's also carotene in leaves of plants. The consumption of plants with carotenoids, especially beta-carotene, will lead to the breakdown product of vitamin A when animals consume these compounds. Beta-carotene is the compound that accounted for this vitamin A type of activity that Steenbock observed. Just as a point of nomenclature, beta-carotene is a carotenoids. I wanted to introduce that term because carotenoids are really a fairly wide range of chemical compounds that occur in plants and some microbes. There's somewhere like 600 different carotenoids in plants and microbes. They're yellow, red or orange in color. Of these 600 some of them, not all, are precursor to vitamin A. That means, when we consume them, when we eat them, they can be broken down to form vitamin A molecules. 

I'll show you how that works in the next slide of so. This subset of carotenoids, these red yellow and orange pigments that can be broken down into vitamin A, are called provitamin A carotenoids. These are vitamin A precursors. Hence the name. In fact, all vitamin A that we have in the human diet and in all animals diets comes from plants, from the breakdown of provitamin A carotenoids. Vitamin A is an essential vitamin. It's necessary that we consume either vitamin A, or in this case, a provitamin A compound, to fulfill this essentiality of vitamin A. We can't synthesize vitamin A on our own. We can accumulate vitamin A. If you eat too many carrots you might turn a little orange. 

Gold fish are gold because of vitamin A. Flamingos are flamingo colored because of carotenoids. Gold fish are gold because of carotenoids. We can store these carotenoid compounds and then break them down into vitamin A at some later time, but we cannot synthesize either the carotenoids or the vitamin A without having the carotenoid there to break it down. This is a very interesting relationship between plants and humans. And I should also say, there's no vitamin A in carrots or sweet potatoes. It's all beta-carotene. It's an interesting relationship that plants provide the precursor. When we eat the plants we get the vitamin benefit. This is a total relationship. 

There's no way around it. A little bit more about the compounds. This is beta-carotene on the bottom. Each half can be broken down into a molecule of retinal or vitamin A. Alpha-carotene, notice that the structure's a little different. The double bond is different on one end. Only one half of it has a vitamin A-type of a structure, so only this end has a vitamin A capacity. Gamma-carotene, again, only one end. These are all carotenoids. Another carotenoid you might be familiar with is lycopene. 

Lycopene gives tomatoes their red color. You see some red, high-lycopene tomatoes on the right, and you see a red carrot on the left. That's also lycopene. A red watermelon is lycopene. These plants are also pigmented by carotenoids, lycopene, but lycopene is not a provitamin A carotenoid. When we eat lycopene it's broken down but not broken down into a retinal molecule. But there are health benefits anyway. Then another example of a carotene up top. So a little bit of background on the range of some structural variation in carotenoids. They're generally about 40 carbons, and those that can be broken down into vitamin A are provitamin A carotenoids. 

Let's go back one step. The point I'm going to make with McCollum's work is why was it that egg yolk and butter where sure good sources of vitamin A as compared to lard and olive oil? We've got a picture of an egg and butter. Lard is white and olive oil actually does have a little bit of carotene. In McCollum's work it's clear that it was actually vitamin A and not the carotenoids that were the source of vitamin A in McCollum's research. But where the vitamin A came from-- Well, in an egg there's both beta-carotene, in butter there is beta-carotene. And there is vitamin A. It was the vitamin A fraction that led to McCollum's discovery, but in fact, eggs and butter also have some carotenes as well. A little bit of thinking some more about this discovery that McCollum made a 100 years ago and in some of the follow-up work that Steenbock made, looking at carrots and some other orange and non-orange plants. With this in mind, since I work on carrots, a question that comes up very often is, why are carrot roots orange? Why is the storage root of carrots orange? We know carotenoids are essential for photosynthesis. All green leaves, including carrots, have carotenoids. 

Without photosynthesis in a leaf-- photosynthesis actually destroys the leaf because the carotenoids have a high antioxidant capacity. We hear about antioxidants for human health. Antioxidants are essential for photosynthesis and helping to pick up some of those biproducts of photosynthesis that can actually damage a cell. Carotenoids are essential for photosynthesis. Plant mutants that have no carotenoids in the leaves have white leaves and can't perform photosynthesis. You have to grow them on a sugar solution. So carotenoids are essential for photosynthesis. That gives us a good idea of why leaves should have carotenoids. In fact, all green leaves do contain carotenoids. There not orange because the green chlorophyll pigments mask the carotenoids. 

But there's no obvious function of carotenoids in roots, at least not from a photosynthetic standpoint. So we come back to the question again, why do carrot roots have beta-carotene? Let's take a look-- I talked a little bit about the domestication of wheat and other staple crops, corn early on. Now let's take a little bit of a look at the domestication of carrots and see if we can some idea of why carrots contain beta-carotene. What can we learn from looking at the historical development of carrots in the history of agriculture? To start with let's look at these wild relatives of carrots. You're all familiar with them. Who here-- I'll ask an easier question. Who here knows what Queen Anne's Lace is? Probably just about everybody. If you don't, this is a picture taken in Middleton in a vacant lot that somebody didn't tend to. This is wild carrot. You can't see the picture here very well, but if you waited long enough, later in the season if somebody didn't cut these wild carrots down in Middleton, you'd come back in September, October and that Middleton vacant lot would look like this. 

This, in fact, is a vacant lot in Tunisia where you can also find wild carrot. In fact, you can find wild carrot pretty much all over the world that there's enough moisture to sustain it. It's a very successful weed. It's not particularly invasive, but it likes to go along with humans. It's likes vacant lots. It likes ditch banks. Wild carrot is, again, the same species as Queen Anne's Lace, the same species as domesticated carrots. Incidentally, why is it called Queen Anne's Lace? Because some of the inflorescence, or flowers, of wild carrot in particular, and actually some domesticated forms too, have purple flowers in the middle of this inflorescence, this collection of flowers. Someone thought that this inflorescence looked like a lacework. And according to some-- I'm not sure how historically accurate it is, but Queen Anne of British history is reputed to have pricked her finger while tatting a round lace napkin. 

The similarity of that blood on that lace to the carrot flower led to the common name of Queen Anne's Lace for carrots. But that's off the story of carotenoids. Let's take a look at wild carrots. You don't see any carotenoids in wild carrot roots. They're white of very, very, very pale orange. Sometimes they're a little bit purple. These are some wild carrots from France. It doesn't matter where you get wild carrots. They all look about the same in terms of that kind of a very branched root, and typical carrot-type leaves and flowers. A little bit of carrot history and also some general carrot facts that tend to come up when we talk about carrots. 

Let's go through these points, some carrot facts. Carrot is the same species as Queen Anne's Lace. You can intercross the two readily. Wild carrot originated first in central Asia, then spread at least 3,000 years ago, to Europe. Wild carrot, now. We know that it spread to Europe in this time frame because there's some ancient human sites from 3,000 years ago where carrot seed is found next to some places where people had set up some camp fires. Probably the carrot 3,000 years ago in Europe, Switzerland, Germany, these sites there, probably carrot was not a cultivated root crop. Probably these were wild carrot seeds that were being used for either herbal medicine or flavoring. Carrot is in the same family of plants as caraway and dill. If you've ever smelled wild carrots you'd see that it has a distinctive odor, not the same odor, but a distinctive odor like dill, caraway, parsley and fennel have. 

Wild carrot, even though it's pretty clear it originated in central Asia, it had already 3,000 years ago spread to Europe. I say already 3,000 year ago because carrots weren't known to be cultivated until about 1,100 years ago. The first reports of cultivated carrots were not white, but rather were yellow and purple. We don't know what happened in this early era of carrot breeding, which we call domestication, that the first carrots were yellow and purple. But the first records of carrots as a root crop were about 1,1000 years ago were they were yellow and purple. I wasn't until 500 years ago that orange carrots were first noted. Some things more unrelated to carrot history. 'Baby' carrots are pieces of large carrots. That question comes up fairly often. If you eat too many carrots your skin can turn orange, but you won't get vitamin A poisoning. 

If you eat too much vitamin A you can get poisoned, but there's a homeostatic control of the breakdown of carotenoids. If you eat a lot of carrots your skin will turn orange, but you won't get vitamin A poisoning. The carrot pigments do improve eye health. Probably lutein as much or more than beta-carotene, but they do promote eye health. The beta-carotene is great for promoting a general strong immunological system. One thing I'll mention is that commercial carrots in grocery stores are a hybrid crop. The hybrid is based on a cross that carrot breeders made in the 1950's with wild carrots. The ability to create a hybrid carrot seed, which I won't go into, is dependant on genes found in wild carrots, in fact, genes of the mitochondrial genome of wild carrots. Every carrot you buy in the grocery store has a mitochondrial genome of wild carrots collected in Massachusetts in the early '50s. There's an interesting connection then between wild an cultivated carrots through this particular feature of the crop. 

Otherwise, carrot breeders have worked hard to get rid of the white color and of the heavy lateral rooting that you see on wild carrots. From a standpoint of geography, central Asia is the region of the Stans, Afghanistan, Pakistan, Tajikistan, and Uzbekistan, in this part of the world. Afghanistan in particular is thought to be where the carrot was first domesticated, and also where wild carrot probably occurred first before it spread over the rest of the world. From central Asia then, we know wild carrots got to Europe 3,000 years ago, cultivated carrot 1,100 years ago. They began moving through human civilizations through the Middle East and the fertile crescent area, through North Africa, and finally got into southern and eventually northern Europe. It also went to the east into India and China, probably not quite so quickly. Then it came over with the first settlers of America from Europe. Again, domesticated about 1,100 years ago, probably in Afghanistan. Purple and yellow were the colors of 1,100 years ago, not orange. Yellow was preferred for it's flavor, but not preferred because it leaves a lot of pigment on your hands when you handle purple carrots. 

It spread, as I mentioned, through the Middle East, North Africa, Europe and also in the east to India and China. It wasn't until orange types were selected, first in either northern Europe or Turkey about 500 years ago. Hybrid work began in the 1950's. So it's pretty modern. Based on written historical records, and there's not an awful lot written in history about carrots. But there are fragments of written history of carrots. That's how we know it's origins in the Afghanistan region. There are yellow and purple carrots mentioned in historical texts in Iran, northern Arabia, Syria, Spain. You see the time frame and the geography moving together, in this case to the west, so that yellow and purple carrots arrived in Europe and Spain about 900 years ago. They got to northern Europe by the 1300's, and 1400's up to England. 

Then around 1500 the first orange carrots were noted in writing, and also in some artistic works. The first American settlers coming from Europe brought, primarily, orange and yellow carrots. In Japan orange and red carrots were developed. It wasn't until the 1700's that carrots were first named. We name varieties of crops commonly today, but there are no reported names until the 1700's. That's a brief history of carrots. We can add carrot photos to the same one with wheat and corn. The time frame is much more recent, starting with wild carrots 1,100 years ago, and moving to the domesticated crop that we have today. In a somewhat similar fashion in the sense that those humans that did the domesticating liked it for traits that were preferential from them. Probably flavor was selected. 

If you eat wild carrots, they're pretty strong. Certainly color and shape were selected in the process of carrot domestication and breeding. So with this wide diversity of carrots that we have in history, we have this range of colors of carrots. Today a lot of people say, look at these brand new purple and yellow carrots. Well, those were the original colors. The orange ones are the new color. It's an interesting crop that we have, not only in terms of the color, but also in terms of the shape. And it also varies for other traits as well. Back to the question though. Why are modern carrots orange? They're orange because they contain carotenoids, but why do they contain carotenoids? We don't know exactly. 

There's no exact record of when or where the first orange carrots occurred. It was probably Europe, but it could have been Turkey. There's a lot of carrot production historically in Turkey. It was probably around the 1500's. Although, there is a little bit of evidence there could have been carrots in the Roman Empire. There's some terminological ambiguity in the word pastinaca, which is the scientific name for parsnip, might have been used for carrot in the Roman Empire. The question was why there wasn't really any remnant of carrots in Europe to go beyond the Romans. So we still hold out the possibility that carrots could have been in ancient Rome, but probably weren't. They more likely started from the European side coming in from the south through Spain. Now the question is why orange became popular. 

There's no written record about that. Is it the food fad of the 1500's? We don't know. One theory I have, and I've got a picture of carrots over here. These are all domesticated carrots except for this white one here. This is actually a wild carrot. Maybe orange became popular because there's two recessive genes that accounted for orange color. If you're growing carrots in you garden for seed, you're going to have a dickens of a time keeping your orange carrots orange in subsequent generations because they're going to cross with wild carrots. It crosses freely with wild carrots with insects. If you're growing carrots for seed in the corner of your garden you're quite definitely going to have crosses with wild carrots. And those crosses with wild carrots look like wild carrots. 

These traits of wild carrots, of the forked root and white color are dominant traits. If you're a gardener, probably women did most of the seed production of vegetables through most of history. If you're growing carrots in the corner of your garden and you've got wild carrots in the vicinity as was the case for most of regions of carrot production in history. There's probably wild carrots nearby. The best way to be sure that the progeny of the seed that you're picking off of your carrots in the corner of your garden is if you've got orange carrots. You know, if you plant seeds and the next generation is orange, you know that that's going to be a cross between a domesticated carrot and a domesticated carrot. If it was out-crossed with wild carrot it would be white and probably taste bad. That might be the reason why orange was selected, but that's just my speculation. We don't really know why orange became popular. Quite certainly it wasn't for health reasons. 

Remember, the first real vague evidence that people had that there was a relationship between food and some of these vitamin deficiency diseases was for scurvy in the 1700's, not for vitamin A deficiency in the 1500's. Regardless of why orange carrots became popular it's fortunate today that modern carrots are orange. Because, in fact, those of you that have heard others in this series talk, there is world-wide a vitamin A deficiency. And it's not a trivial deficiency. Vitamin A is an essential nutrient. There's no alternative in our diet to vitamin A, except maybe carotenes but that's really vitamin A in the end. It's not common that it's a deficiency disease in more developed countries, but it is often referred to as a shortfall vitamin. We should probably be eating up to 20%, 30% more vitamin A in the US diet than we are eating today. There's certain sub-populations in the US, some ethnic groups with teenage populations that are really at risk for vitamin A deficiency, but physicians don't commonly report it. One thing that I'll mention sort of as an aside is not only are we shortfall in terms of vitamin A intake, we're really shortfall in terms of fruit and vegetable intake. 

If we ate our fruit and vegetables as in fact we should be, according to the USCA recommendations, we certainly wouldn't have any vitamin A deficiency. That's in some ways a secondary topic, but I just wanted to mention it. Outside of the shortfall deficiency of Vitamin A in the US, in the developing world vitamin A deficiency is in fact a significant problem. In terms of organic nutrient  deficiency, it's the most frequent one after protein energy deficiency. Some mineral deficiencies are more common. There's estimated to a quarter of a million sub-clinical deficient children a year. This deficiency leds to reduced immune function, which means low disease resistance. Something like measles is usually fatal for these kids. Along with even more extreme vitamin A deficiency comes permanent blinding. It's estimated that between a third and half a million people, generally children, die every year from vitamin A deficiency. 

There is a need for more vitamin A, not only in the US where we have a pretty good supply, but in the rest of the world as well. Looking at carrots, we really have an example of-- when we're looking at improving carrots as a source of vitamin A. It's really an example of an agricultural intervention for a health problem. At least it's a model for this. In fact, if we look at the nutritional history of carrots in the US, it's a pretty good history. This is based on some of the food data that's been collected back to the earlier 1900's. Carrots in the 1950's were estimated to have 60 parts per million carotenes. I'm not going to-- exactly what that means-- I relate it to how much carrots you need to eat down here. But just looking at the numbers, in the '50s the average carotene content, and these were orange carrots, had 60 parts per million. In the 1950's that was the average carrot. 

By the 1970's the first hybrid carrots had 90. Today carrots have 130 to 140 parts per million carotene. Carrots are mainly alpha and beta-carotene. Both of those are provitamin A carotenoids. They're good vitamin A sources. In fact, a modern carrot today provides enough provitamin A to provide an adult with their vitamin A requirements for the day if that's the only source of vitamin A you ate. And in fact, if you look at a square meter of carrots, one crop in a year is enough for an adult to have enough vitamin A for the full year if that was your sole source of vitamin A. It's a very rich source of vitamin A. That comes from the provitamin A carotenoids of carrot. In fact, there's been an increase of carotene content in recent history in the US. 

The reason for this is because of the plant breeders. Some work, in fact, initiated primarily here at Wisconsin. Warren H. Gabelman was on the Hort. faculty. He's still around. He and Clint Peterson, who at the time was in Michigan. Eventually Peterson moved over here to the University of Wisconsin as well. Peterson hired me. Between the two of them they really began the hybrid carrot industry in the US and developed a carrot breeding stock that all of the seed the industry depends on. We continue developing those carrots yet today. Hybrids are important for carrots because of the uniformity that comes with hybrids. 

If you're growing a commercial crop uniformity is a good thing. Along with that uniformity Gabelman and Peterson also selected for uniform orange color and orange cores, as opposed to yellow cores. Some carrots have yellow cores. If you've grown some carrots from seed that's 40 years old, much of it has yellow cores. What Gabelman and Peterson did was to not only start the development of carrots as a major commercial vegetable crop in the US, but also they did some important work to enhance the nutritional quality and productivity of carrots. I'll mention too that Gabelman discovered two genes I'll talk about later, the Y and Y2 genes. What are yellow cores? This isn't actually the worst yellow core picture you can find. If you've grow carrots sometimes you'll notice the internal core is yellow. That's viewed as a defect by carrot breeders. You will still see yellow cores in commercial hybrid carrots, but most hybrid carrots are orange in the core rather than yellow. 

That's one of the traits that carrot breeders have selected for, at least since the 1950's. Uniformity is the other thing that comes with hybrids. You just generally don't find that kind of uniformity with open pollinated carrots. It's possible, but it's easier with hybrids. With Gabelman and Peterson's work the road to increasing carrot productivity, and also the carotene content began, because of their work to select for a higher orange color. We've done some more recent work to see how high we can go in selecting carotene content in carrots. The average US carrot is the color of the carrots in the middle here. They're about a 140 parts per million. We've done some breeding work for five or ten generations from a couple of different breeding populations. In one population we roughly doubled the carotene content after four or five generations. 

In another population we tripled the carotene content. You still see these are orange carrots. They're more orange. It's possible that we could have-- In fact work we have today is to look at moving forward at increasing carotene content, to some extent, in carrots as well. We're probably more interested in improving flavor than increasing carotene content at this point, but we are continuing to do some work to increase carotene content of carrots. It's a great source of vitamin A because of these orange pigments that plant breeders have and continue to work on selecting in breeding programs. Well, you can breed for higher carotene content. We've been doing that quite a while, but the question is, if you breed for higher carotene content with two or three times as much carotene, does that really deliver two or three times as much vitamin A to a consumer? That's where Sherry Tanumihardjo comes on the scene. She, I guess, gave a talk in this series earlier this year. With Sherry's work she demonstrated that higher carotene content, when people-- This is a human trial. 

When people eat high carotene carrots the serum carotene level is higher than it is for average carrots. This was great work from my standpoint because it demonstrated that the breeding work that we did to increase carotene content in fact is delivered to us as consumers when we eat more high carotene content. Sherry also did some very interesting work to demonstrate that other pigments in other colored carrots are bioavailable, which means when we eat these different colored carrots the pigments do in fact get into our serum. Lycopene in red carrots, lutein in yellow carrots, anthocyanin in purple carrots. I won't say a lot about these other colors because the main focus is vitamin A today. But these other pigments that are in purple, red and yellow carrots also has nutritional benefits. Provitamin A has a vitamin A precursor important for immune function. Purple pigments are not carotenoids, but they have important antioxidant activity. Lycopene, as I mentioned before, is a carotenoid, but a provitamin A carotenoid. It's associated with reduced incidence of some forms of cancer. 

And Lutein, another non-provitamin A carotenoid in yellow carrots, is important for eye health to prevent macular degeneration. With Sherry's work we find out that these carrots of different colors in fact deliver the pigments we've been breeding for in these different colors. In fact, today carrots are the single most plentiful source of provitamin A carotenes in the US diet. They're 58% of the total. The second after carrots is sweet potatoes, the third is tomatoes, and a little bit from a few other crops. Overall, carrots provide between 20% and 25% of the vitamin A in the US diet. That is really quite remarkable considering we don't eat that many carrots compared to some of the staple foods. This understanding of-- Well, with this work on developing higher carotene carrots, the question is what's going on biologically, biochemically, that accounts for carotene accumulation. Can we take this information and apply it to other crops? Here's a brief overview of some other work underway. There's two major genes that account for the color differences between white carrots or wild carrots, and yellow carrots and orange carrots, the Y and the Y2 genes that Gabelman discovered. 

Wild carrots have two dominant genes, orange carrots have two recessive, and yellow have one dominant and one recessive based on Gabelman's work. Where we've come with this is we've been able to map these Y and Y2 genes so we can do genetic studies to follow genes, and place the genes on genetic maps. Why is that important? I'll tell you in a minute. We also know where these pigments are in the biochemical pathway, that lycopene is earlier in the pathway. This is the carotenoid biosynthetic, a part of it, alpha beta-carotene in the middle, Lutein further down. There's a group of other very important compounds below this not indicated, but the major pigments of carrots are shown here. We know where the genes are. We know what the enzymes are. Where we're at right now is, as we're sequencing the carrot genome we've identified candidate genes for the Y2 gene. What does that mean? A candidate gene is a gene that is located on the genetic map where this Y2 trait shows up. 

In other words, yellow verses orange color. The idea there is to understand what the function of this gene does. The idea beyond that then is, can we take this information and apply it to other crops? Furthermore, this is interesting to just help us understand how carotene is metabolized in carrots. If we look at the sequence of these genes over some of these wild and domesticated carrots from over history maybe we can get some ideas of the historical sequence of the domestication of carrots from this genetic database. This is why we're interested in studying these genes of carrots. What have we learned from carrot breeding and genetics? To breed a more nutritious crop, well, there are similar genes in other crops. I'll show you some pictures. I already showed you different colors of corn, yellow and white. There's genes in potatoes and wheat and a range of other crops that can lead to carotenoid accumulation in other crops like they can in carrots. Can we apply what we're learning in carrots and carotene to other crops? One thing I will point of that we've learned is that growers get no economic value from high carotene carrots or other crops. 

We buy food based on price and flavor. Maybe once of twice we'll try something because it's more nutritious. I guess a lot of people eat carrots because they're mother or father told them to. If you forgot that, you otherwise might not eat your carrots. Growers really get no added value for the crop. We're breeding for higher carotene for the consumer without bringing any added value to the grower, so what the grower can get added value for though is better flavor. We've been working hard at trying to genetically improve the carrot flavor. We've made some progress. I'm sure if I polled you, you would have horror stories of carrot flavor and tell me what I should be doing different. Please do. 

We're working on it. It is something that we also breed for, and we're putting a lot of focus on. We'd like people to eat more carrots, partly because the growers can make more money, but because we should be eating more vegetables. Along the way we'll consume more carotenes. There's a pretty good association between low consumption of fruits and vegetables and the incidence of obesity in the US, and around the world. There's been good progress for breeding for yield and farm value of pretty much all crops, but hardly any progress in breeding for nutritional value of crops. I gave you an example of carrots, but there's very few crops where the nutritional value of the crop has gone up in time. That's probably because there isn't this impetus from the standpoint of grower value for more nutritional value. But we really should be working on breeding for more nutritional value, and we have great opportunity in a range of other crops. Not only the provitamin A carotenoids, but there's wide genetic variation for vitamin C level in not only citrus, but other crops, genetic variation for folate level in beets, B vitamins in leafy green vegetables, for minerals in broccoli and legumes, and a range of antioxidants in many crops. 

A challenge with this kind of research is, we in agriculture, need to work with people in health sciences, which actually a lot of fun, but it's something that doesn't happen as often as it ought to in Ag. research. Here's some examples of variation in provitamin A carotenoids. These are sweet potatoes. You can see some are high carotenoid and some are no carotenoid. These are bananas over here, orange bananas from New Guinea. Then what we'd call regularly colored bananas are the rest on the plate. There's papayas, and this is not a melon, this is a cucumber. There's also potential for orange cucumbers. There's genetic variation that is out there in crops that breeders can capitalize on, and I would say should be capitalized on. 

For high carotene carrot today, it's been a pretty successful story. Not because of high carotene, but carotene levels have gone up in the last 40 years and, actually, per capita consumption has gone up in the last 40 years. More so because you an I prefer baby carrots because of that hard work of cutting and peeling a carrot. [laughter] We buy them and pay twice as much for them, and we eat more carrots because of it. As a consequence of the higher carotene content and the higher per capita consumption carrots do account for a higher part of the vitamin A in the US diet today. Furthermore, carrots are worth more to growers today than they were 40 years ago. It's a good success story for everybody. To recap some of the things I've talked about, domestication of plants and animals is a significant achievement. Agriculture is something that we're stuck with. We can't go back. 

To feed us, the only way we have is agriculture. We're dependant on domesticated plants today. The discovery of vitamin A really epitomizes this very interesting connection that humans have with the crops that we eat. Essential vitamins coming from a pigment and the discoveries made here with vitamin A are really neat and really interesting. We should be eating at least a three-fold amount of fruits and vegetables as what we do. So in addition to breeding for better nutritional content we ought to be doing something to induce us as consumers to eat more fruits and vegetables. I think flavor is the way to go. If you've got any ideas on how to make a crop more convenient it'd probably be worth a lot of money too. Baby carrots is a good example. Can we take what we've learned about breeding carrots and apply it to other crops? And what can we do to improve carrots for human consumption to make them more appealing? These are important questions we are working on. 

I really feel we have a responsibility as agricultural scientists to work on increasing food quantity and quality. There's still going to be starvation and malnutrition, and it's probably only going to get worse, but we need to do what we can do in agriculture for the good of the cause in general. These are complex problems that really take a multidisciplinary approach. The research that we do is multidisciplinary and requires a team, just like this team. In fact, this team is a group of farmers in the 1850's in Wisconsin. This isn't really me at the beginning of my career. [laughter] But the team that supported our work is graduate students. I've been lucky enough to be here and train grad students and also support staff, and also have funding sources to do the work. With that I would take any questions if there's time. Thank you. 

[applause]