Plant an apple seed from the juiciest apple you ever ate, then sit back and wait ten years. You might move away in the meantime, but you won’t forget your little apple tree. Take a pilgrimage to see the result of your patience: ripe apples. They’ll look a little different from that memory of ten years ago, but bite into one and… euugh! Spit it out and stare in horror.
The saying is wrong; the apple always falls far from the tree. Every seed in every apple contains a different combination of genes from its two parents, and only occasionally does the crossing result in a tree with a good tasting apple.
It’s a problem that was solved thousands of years ago by grafting. Apple growers discovered they could dispense with seeds by inserting a twig with a bud from a desired tree into the base of a less desirable tree with the top cut off. The resulting apples, barring mutations, would all be as delicious as those from the first tree. It was an early form of cloning still in use today.
Of course, we have now taken things to extremes. North America was once home to 15,000 varieties of apples, grown both for eating and for making hard cider. Prohibition, marketing, and the demand for apples that look pretty on a supermarket shelf, have all helped to slash that number. Today, just 15 varieties represent 90 percent of the market. Red Delicious, first found in 1870’s Iowa, represents a staggering 40 percent of the market, each apple as red as the last.
While clones, and clones of clones, may have won over the apple market, they have surrendered the battle with pests and diseases. Powerless to adapt, the trees come under fire from pests that have had many generations to experiment with different means of attack. We, the apple protectors, do battle on their behalf with pesticides.
Cloning isn’t unique to apples, and the apples we buy do at least still have seeds. Think of the fruits we prefer seedless. The navel orange, for example, is sterile. Each orange contains within it a partial second orange, which looks like a belly button. The navel orange arose from a mutation in a tree in the grounds of a Brazilian monastery in the early 1800’s. Thanks to grafting, that 19th-century mutation is in a store near you even now.
The banana is another example of human intervention. Have you ever seen a banana with seeds? They look tricky to eat, which is why people have long preferred the seedless version. These arise naturally, once in a while, when a banana plant inherits three sets of chromosomes from its parents instead of one from each. Three chromosomes can’t divide evenly, and the resulting plant is sterile and seedless. When side shoots called suckers emerge from such a plant, they can be replanted to grow a clone. Once again, the clones are no match over time for pests and diseases, something banana growers and consumers learned the hard way when the Fusarium fungus caused widespread Panama Disease and wiped out the popular Gros Michel banana during the 1950’s and 1960’s.
We could have learned a lesson, and replaced the Gros Michel banana with several different varieties, but the pressure to provide a perfect banana led us to repeat our mistakes. So while people in parts of Africa and Asia continue to grow many varieties of banana for their own consumption, virtually all exported bananas today are one variety, the Cavendish.
Of course, the fungus that did for the Gros Michel has mutated to catch up with the Cavendish, and has been joined in its efforts by another fungus called black sigatoka. The current answer is merely to spray the plants a couple of times a week with fungicides, accounting for about 30 percent of the production costs. These fungicides harm the soil and cause pollution, which means that sooner or later we will have to accept a different banana variety. Who knows if it will be as straight, as yellow, or as resistant to bruising as the Cavendish, but one thing is certain - it will be a clone.
Further reading:
The Botany of Desire, by Michael Pollan, 2001
How the apple took over the planet, Salon
With the familiar Cavendish banana in danger, can science help it survive? The Conversation
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| Mutsu - my favourite:-) |
It’s a problem that was solved thousands of years ago by grafting. Apple growers discovered they could dispense with seeds by inserting a twig with a bud from a desired tree into the base of a less desirable tree with the top cut off. The resulting apples, barring mutations, would all be as delicious as those from the first tree. It was an early form of cloning still in use today.
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| Apple tree grafting/ by Karelj |
While clones, and clones of clones, may have won over the apple market, they have surrendered the battle with pests and diseases. Powerless to adapt, the trees come under fire from pests that have had many generations to experiment with different means of attack. We, the apple protectors, do battle on their behalf with pesticides.
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| The navel orange's navel |
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| Navel orange with second orange at the bottom |
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| Banana with seeds/Mkumaresa/CC BY-SA 4.0 |
The banana is another example of human intervention. Have you ever seen a banana with seeds? They look tricky to eat, which is why people have long preferred the seedless version. These arise naturally, once in a while, when a banana plant inherits three sets of chromosomes from its parents instead of one from each. Three chromosomes can’t divide evenly, and the resulting plant is sterile and seedless. When side shoots called suckers emerge from such a plant, they can be replanted to grow a clone. Once again, the clones are no match over time for pests and diseases, something banana growers and consumers learned the hard way when the Fusarium fungus caused widespread Panama Disease and wiped out the popular Gros Michel banana during the 1950’s and 1960’s.
We could have learned a lesson, and replaced the Gros Michel banana with several different varieties, but the pressure to provide a perfect banana led us to repeat our mistakes. So while people in parts of Africa and Asia continue to grow many varieties of banana for their own consumption, virtually all exported bananas today are one variety, the Cavendish.
Of course, the fungus that did for the Gros Michel has mutated to catch up with the Cavendish, and has been joined in its efforts by another fungus called black sigatoka. The current answer is merely to spray the plants a couple of times a week with fungicides, accounting for about 30 percent of the production costs. These fungicides harm the soil and cause pollution, which means that sooner or later we will have to accept a different banana variety. Who knows if it will be as straight, as yellow, or as resistant to bruising as the Cavendish, but one thing is certain - it will be a clone.
Further reading:
The Botany of Desire, by Michael Pollan, 2001
How the apple took over the planet, Salon
With the familiar Cavendish banana in danger, can science help it survive? The Conversation
Wow, never saw w banana seed before.. always thought they were those tiny brown specks..!
ReplyDeleteThe tiny specks are undeveloped seeds. They'd never mature to become viable.
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