How to turn cotton into a food crop

By Ed Yong | October 1, 2008 10:00 am

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Blogging on Peer-Reviewed ResearchThe world is currently home to 6.5 billion people and over the next 50 years, this number is set to grow by 50%. With this massive planetary overcrowding, Band Aid’s plea to feed the world seems increasingly unlikely. Current food crops seem unequal to the task, but scientists at Texas University may have developed a solution, a secret ace up our sleeves – cotton.

Cotton.JPGCotton is famed for its use in clothes-making and has been grown for this purpose for over seven millennia. We do not think of it as a potential source of food, and for good reason. The seeds of the cotton plant are rife with a potent poison called gossypol that attacks both the heart and liver. Only the multi-chambered stomachs of cattle and other hooved animals can cope with this poison, relegating cottonseed to a role as animal feed.

Getting rid of gossypol could contribute towards reducing the world’s hunger crisis. A fifth of a cottonseed’s weight is made up of oil, and a quarter of high-quality protein, and for every kilogram of fibre, each cotton plant produces 1.65 kg of seed. The plant is a worldwide crop, grown in over 80 countries by some 20 million farmers, the majority of whom live in the poorest parts of the world where starvation is an ever-looming threat. If only the seeds could be made edible.

In 1954, scientists attempted to launched a programme to cross-breed normal cotton plants with a mutant strain that lacked the glands that make gossypol. Unfortunately, they discovered that cotton creates the poison for a reason – it protects the plant’s tissues from insect pests and infections alike. The programme’s seeds were safe for human consumption, but the weakened plants readily succumbed to insect attacks, destroying their commercial potential.

Ganesan Sunilkumar and colleagues at the Institute for Plant Genomics and Biotechnology have solved the problem. They used a technique called RNA interference, or RNAi, to turn off a gene which is essential for gossypol production, called delta-cadinene synthase. But their trick was to put their system under the control of a genetic switch used only in cotton seeds, and not the rest of the plant. As a result, levels of gossypol plummeted in the plant’s seeds and these alone. The rest of its tissues remained as resistant as ever to attackers.

Gossypol.jpgSunilkumar ran his special plants through a series of tests to make sure that the RNAi’s effects never spread from the seeds to other organs. The plants passed every one and best of all, they stably passed on their characteristics to their daughters. This study is testament to both the power and the precision of modern genetic technology. The researchers identified a very specific point in a biochemical pathway and blocked it in a single part of the plant. The result is a variant that retains the original’s survival abilities, but is suddenly fit for human consumption.

Their approach has tremendous potential for opening up other food sources. For example, the beans of the tropical grass pea, Lathyrus sativus, are often eating by poor people in Africa and Asia in times of dire need. As the beans contain a potent neurotoxin – a nerve poison – those eating them often contract a neurological disease called lathyrism. With Sunilkumar’s technique, lathyrism could become a thing of the past.

For those who feel that the use of such technology is tantamount to playing God, consider this. Every year, 44 million tons of cottonseed are wasted. With this new technology, the engineered seed could provide enough protein for half a billion people every year.

Reference: G. Sunilkumar, L. M. Campbell, L. Puckhaber, R. D. Stipanovic, K. S. Rathore (2006). From the Cover: Engineering cottonseed for use in human nutrition by tissue-specific reduction of toxic gossypol Proceedings of the National Academy of Sciences, 103 (48), 18054-18059 DOI: 10.1073/pnas.0605389103

Comments (11)

  1. Jim Thomerson

    When I was a young person out on the ranch in the 40′s, I routinely ate cottonseed cake pellets we bought for livestock feed. Po’ folks used cottonseed meal for flour in making bread. I don’t think I am a ruminate. Obviously economical methods for depoisioning cotton seed have been around for a long time. So what is the point?

  2. Jim Thomerson

    As I recall the cotton seed pellets were @ 40% protein. There were also peanut pellets made of whole ground peanuts, hull, sand and all. There were soybean pellets which I did not care for. I think both these were considered to be inferior feed, compared to cotonseed pellets. If we farm cotton with non toxic seed, how long will it take various pesty little critters to figure out that they are good to eat?

  3. oscar zoalaster

    Mr. Thomerson states that:
    When I was a young person out on the ranch in the 40′s, I routinely ate cottonseed cake pellets we bought for livestock feed. Po’ folks used cottonseed meal for flour in making bread. I don’t think I am a ruminate. Obviously economical methods for depoisioning cotton seed have been around for a long time. So what is the point?”
    1.) How frequent, and in what quantity – per day and in aggregate – was your consumption? What is the minimum dangerous dose of gossypol, again per day and in aggregate? How much individual variation is there in susceptibility to gossypol damage?
    2.) That some people eat something poisonous without observed ill-effects does not demonstrate that any method, economical or not, exists to de-poison cotton seed meal. Since you assert such methods exist, what economic methods are there for de-poisoning cotton seed meal?

  4. Jim Thomerson

    I am 73, and I don’t remember exactly. I would make a reasonable guesstimate that betweem the ages of 6 and 18, I ate maybe 4 to 6 oz of cottonseed pellets three or more times a week. My father didn’t like it because he didn’t think the pellets were necessarily manufactured under sanitary conditions, but I didn’t pay any attention. An occasional pellet would have a musty taste and I would spit it out. I thought maybe a rat had peed on it.
    As to how the pellets were processed, I have no idea. Google might be a help. There were no “Not for Human Consumption” warnings on the tags or sacks.

  5. It’s funny how every school child, at least of my generation (late 30s), knows who Eli Whitney is and what he invented: the cotton gin. But he never made a dime off of it.

  6. El Christador

    Slick.
    I understand the literature indicates that coating it with chocolate doesn’t work so well for rendering cotton fit for human consumption.

  7. heh, this reminds me of that bit in catch 22 when Milo ends up buying the entire egyptian cotton crop and tries to turn it into food by covering it in chocolate :)
    Very interesting post.

  8. Jim Thomerson

    Looked up information on feed for farm raised catfish. Comment was that 10-15% cottonseed meal could be used, but it was low in lysene due to binding. If higher percentages were used, lysene supplement was needed. About the same percentages and lysene supplement recommended for peanut meal.
    How about genetically engineered cotton with a higher percentage of lysene in the seeds?

  9. Tsu Dho Nimh

    Jim – Feed standards limit the amount of gossypol that can be in the cake because it’s toxic. You would have had to eat quite a bit more.
    The cake is what’s left after pressing the oil out, and much of the gossypol ends up in the oil, which has to be refined before it’s used. If not, it is toxic coking oil.

  10. Mu

    Hmm, since the cotton seed is useful as animal feed, therefore freeing up soy and corn otherwise wasted as animal feed, what’s the exact net gain in food available for human consumption?

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