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genetic engineering

The plan on genetically engineered crop info

I tried to tackle it a couple of times over the weekend and ended up being intimidated by the amount of info, and also discouraged at the though of few people would want to read all the way through a long treatise on the subject.

So here’s what I’m going to do instead. Every morning at ~2 AM Pacific Time, a summary of a new genetically engineered crop will be posted on the site. The first one, Canola, should have come out this morning. (Please let me know about any mistakes you spot, or cool facts I didn’t mention.) Once there’s a post for every crop that’s currently genetically engineered, I’ll write up an actual page on the subject with links to all the relevant posts. Anyone who’s interested can point out anything I’ve written that is unclear or misleading, and then a link to that page will go up at the top of the site, next to “home” and “about”, to serve as a resource for anyone who needs it.

Predictable Spinning of Squash

I dont have any picture of pumpkins handy, so this watermelon (and fellow cucurbit) will have to do.

I don't have any picture of pumpkins handy, so this watermelon (and fellow cucurbit) will have to do.

What could be a more fitting topic for a Halloween post than cucurbits, the family of plants that (in addition to crops like watermelon and cucumber) include squash and pumpkins? Yeah, I know it’s a stretch.

A week ago a paper came out in PNAS (the proceedings of the national academy of sciences. A very prestigious journal, one step down from Science or Nature), that showed when an artificially inserted gene in squashes that provided virus resistance was introgressed into a wild related species it actually made them less fit. Short version: the wild squash also suffer from the virus which attacked domesticated squash but are also attacked by beetles, and the beetles prefer to eat squash without the virus. Tomorrow’s Table has a much better and more complete explanation of the research.

In that post the very first commenter predicted the result, that in this particular case a transgene (like most genes involved in domestication) was beneficial for farmers but not for wild plants, would be spun into “another failure for GMOs” when the real message is “we were worried about pollen drift, but in this case it turns out we didn’t have to be.”

He was right. (more…)

Banana Biology

When I was giving my lecture to on phylogeny and tetraploidies, I found out not everyone knows why bananas don’t have seeds.

The reason the bananas we eat don’t have seeds is that they are all sterile. A long time ago the Cavendish bananas first came into being when a tetraploid banana (that is a plant that has four copies of every chromosome instead of the normal two) mated with a normal diploid banana. The result, a banana with three copies of every chromosome couldn’t mate or produce seeds. One of the steps in making reproductive cells (the analog of human sperm and egg cells) is the even dividing of a plant’s chromosomes into two reproductive cells.* Normal diploid cells can easily divide into two cells (one copy of each chromosome in each cell), tetraploid plants can divide the same way (two copies of each chromosome in each cell). Hexaploid, three copies in each and so on. Odd numbers of chromosomes don’t work. The plants can’t successfully make the cells it needs to reproduce, if it can’t reproduce it can’t make seeds, and that is why bananas (or seedless watermelons) don’t have seeds. (more…)

GM Tomatoes Don’t Taste Bad

Spear Thisle

Photo Dalboz17, Flickr

I can’t count the number of times I’ve run into someone either online or in person who is convinced genetic engineering makes food taste bad. “Just try an organically grown heirloom tomato,” they will say, “it’s so much juicier and tastier than those GM tomatoes you buy at the grocery store.” It is a great way to win support since many people listening to or reading those words will have had a similar experience tasting a oddly shapped and colored heirloom tomato and barely believing it to be the same fruit* as the perfectly shaped ones lining the aisles of every grocery store. Heck, even I agree they taste better, and I never grew out of not liking tomatoes in the first place. Score one for the opposition to genetic engineering. Or it would be if the tomatoes down at your local grocery store weren’t completely untouched by genetic engineering. GM Tomatoes don’t taste bad and you’ve probably never eaten one in your life (more…)

Herbicide Resistance

Plant breeders can find natural resistance to pathogens. Some crops can be grown in regions where they have few or no natural insects attackers. But every crop with face the problem of weeds, other plants that threaten to steal light and nutrients. And the crops that sustain us will always suffer from an unfair handicap, as crop plants devote much of their energy to food production (whether that means fruits, roots, seeds, or even leaves) while weeds can devote all their energy to outcompeting their neighbors.
Since farmers as individuals and we as a species depend on growing fields of crops like like corn, eggplant or rhubarb and not weeds like kudzu, thistles or chickweed we need to protect our crops. A farmer can protect his crop physically, either sending people out with hoes to slay every plant but his own crops* or using a cultivator to turn over the soil between the rows, hopefully burying or slicing and dicing the majority of the weeds. The first costs money and is miserable for whoever does the work. The second burns extra fuel, bad from both global warming and cost perspectives, and increases soil erosion (top soil broken up by the plows of the cultivator can more easily be carried away by rainfall).
The alternative is for the farmer to defend his crop with herbicides (plant killing chemicals). The problem with this approach is to find chemicals that kill weeds but not the crop plants. Similar to the challenge of finding antibiotics which can kill the bacteria attacking a human body without killing the human her or himself, herbicide developers face the added difficulty that most weeds are much more closely related to the crops they’re competing with than bacteria and humans(which last shared a common ancestor more than a billion years ago). In many cases it is more comparable to finding a toxin that would kill mice, but not humans, at similar dose to body-weight ratios. And even when they find a suitable herbicide, it may have nasty effects on humans (and many herbicides do).
Herbicide resistant lines are can survive broad spectrum herbicides, herbicides that kill all plants, like glyphosate (Round-up when you the brand name version from Monsanto), glufosinate (Liberty) and Imidazolinone (Beyond). Without having to worry about finding chemicals naturally survivable by crop species, herbicides can be used that are far more effective at killing weeds, in addition to being less toxic to humans.** With more effective pesticides, farmers can stop using cultivation as an additional method of weed control, letting the soil remain unbroken, which reduces the loss of topsoil from erosion. The mistake I think a lot of people make is assuming all herbicides are equally bad. Given the choice I’d much rather get lost and wander into a field treated with glyphosate than a field treated with a quarter as much atrazine.
*The worst sunburn I ever got in my life came from a day spend hoeing a cornfield
**The MSDS for the active ingredient in round-up, glyphosate. Basically you shouldn’t rub it in your eyes or take a bath in it, but even then, the result would probably be irritation, not death. Extropolating from the LD50 in rats***(with apologies for nested footnotes), always a dangerous thing to do, a person of my weight would have to eat 500 grams of pure glyphosate to have an even chance of death. And that’s on top of it being classified as Group E (evidence that the chemical does NOT cause cancer)
***LD50 is a fancy way of saying how much of a toxin must be feed to a group of lab animals to kill half of them.

What herbicide resistance is, and why the trait is so valuable to farmers.

Spear Thisle

One of many enemies faced by crops, the spear thistle. Photo John Tann, Flickr

Plant breeders can find natural resistance to pathogens. Some crops can be grown in regions where they have few or no natural insects attackers. But every crop with face the problem of weeds, other plants that threaten to steal light and nutrients. And the crops that sustain us will always suffer from an unfair handicap, as crop plants devote much of their energy to food production (whether that means fruits, roots, seeds, or even leaves) while weeds can devote all their energy to outcompeting their neighbors.

(more…)