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  • [ intro ]

  • One of the most extraordinary things about dogs

  • is how different they all are.

  • Like, we took one wolfy species and made over 200 breeds

  • from adorable wrinkly pugs to lanky, powerful greyhounds.

  • And we didn't just do this kind of whole-body-tinkering with dogs.

  • We've done it with plants, too.

  • Just about all the fruits and veggies you can buy at the supermarket

  • have been shaped by human breeding.

  • Most look totally different than their wild ancestors.

  • But there's one plant species that's produced

  • so many different varieties that it's known to biologists

  • as 'the dog of the plant world'.

  • You probably know it as kale.

  • And broccoli.

  • And cabbage.

  • And brussels sprouts.

  • T

  • hat's right, those are all the same species of plant.

  • Foodie favorites like kale and cauliflower

  • are just a couple of the cultivars,

  • or human-modified and grown varieties, of Brassica oleracea.

  • There are dozens more,

  • from the logarithmic spiral of romanesco broccoli to the distinct,

  • pointed shape of caraflex cabbage.

  • And you might think tons of variety is just

  • what happens when humans selectively breed something for generations.

  • But that's not entirely true.

  • After all, we've been growing and breeding lettuce

  • for about the same amount of time,

  • and yet, all lettuce varieties look pretty lettuce-y.

  • It turns out that B. oleracea is kind of a special plant.

  • It was so transformable because it underwent some massive genomic event

  • during its evolution.

  • The story of why we have such a variety of this kind of plant

  • starts millions of years ago.

  • Back then, an ancient Brassica ancestor did something quite remarkable

  • it tripled its genome.

  • That massive genome was whittled back down to a more reasonable size

  • by the time wild cabbage emerged

  • as its own species about four million years ago.

  • Still, it meant that wild cabbage ended up with a lot more genetic variation

  • than your average garden plant.

  • You see, broccoli and kale and brussels sprouts don't just look different.

  • They're very genetically distinct, too.

  • And we're not just talking little tweaks to genes.

  • In a 2016 paper, researchers sequenced

  • the genomes of 9 different cultivars to construct the plant's pangenome

  • the total genetic variation that exists in the species.

  • And they found nearly 20% of the genes in that pangenome

  • are only present in some varieties.

  • So not only do cultivars have a lot of mutational differences,

  • they also have whole genes that aren't present in other members of their own species,

  • even though they all came from the same wild cabbage.

  • That plant, as far as we can tell,

  • originated in the coastal areas of southern and western Europe.

  • We don't know exactly when our species first grew and domesticated it,

  • but genetic evidence suggests it may have been around 2000 B.C.E.

  • The earliest written records come from ancient greece,

  • and they suggest the first cultivars were leafy

  • veggies like kale and collard greens.

  • And the Greeks weren't the only ancient people who tinkered with wild cabbage.

  • Scientists are pretty sure that the plant was domesticated many times in several locations.

  • Some of these domesticated varieties found their way back into the wild,

  • became feral, and then were re-domesticated,

  • adding even more to the species' genetic diversity.

  • And all that genetic diversity eventually allowed people

  • to magnify different structural parts of the plant.

  • The variety we now call cabbage, for example,

  • seems to have arisen sometime before the tenth century

  • when people bred a kale-like plant to have larger buds on the tips of its stems.

  • Brussels sprouts are also enlarged buds

  • the buds that grow all around the length of the stem.

  • And scientists aren't quite sure when the cultivar first emerged,

  • but it was definitely being grown in Belgium by the end of the 18th century.

  • Then there's kohlrabi, which literally means cabbage turnip in German

  • presumably referring to its bulb-like enlargement at the base of the stem.

  • It's not clear when it first came about, either,

  • but historical literature suggests it was grown throughout Europe by the 1500s.

  • Then there's broccoli and cauliflower.

  • Both get their unique floretsthe yummy parts we eat

  • from mutations to flowering genes.

  • In broccoli, those mutations lead to a lot of flower buds packed tightly together.

  • Cauliflower has a lot of tightly packed flowering structures, too,

  • but most of them never actually flower.

  • Instead, the white, pre-bud flower tissue replicates itself as it grows,

  • leading to the familiar, curd-like head.

  • Since both have modified flowers,

  • it's thought that one came from the other, but it's still not totally clear which came

  • first.

  • As of 2018, genetic research seemed to be leaning toward team broccoli.

  • In fact, scientists are still trying to piece together

  • how we got all of these amazingly different versions of Brassica oleracea

  • and in what order.

  • Trouble is, the same genomic shuffling events which gave this species so much genetic diversity

  • also make it challenging to figure out a precise timeline for these cultivars

  • and their relationships to each other.

  • Researchers are eager to figure out as much of that as they can,

  • because it will also help them better understand how the different varieties tolerate different

  • environments,

  • resist different diseases, and produce different nutrients.

  • You see, by better understanding these nutritious, delicious,

  • and fascinating dogs of the plant world,

  • scientists just might figure out how to make our favorite crops more hardy, sustainable,

  • and nutritious.

  • If you think these flexible plants are incredible,

  • I bet you'll like our episode on eight plants that have mastered the art of deceit.

  • And we've got so much more mind-blowing science to tell you about!

  • We put out a new video here on SciShow every day.

  • And if you click that subscribe button and ring the notification bell, you won't miss

  • a single one.

  • [ outro ]

[ intro ]

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羽衣甘藍、花椰菜和球芽甘藍是同一種菜品 (Kale, Cauliflower, and Brussels Sprouts Are the Same Species)

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    林宜悉 發佈於 2021 年 01 月 14 日
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