Seedlessness?
March 4, 2018 10:22 AM Subscribe
Why do some clementines have seeds, yet no commercial bananas seem to? What determines when a clementine will have seeds? Do they come from seedy trees, or randomly from any blossom, or from a particularly seedy branch? Seems to me a tree should either bear seedy fruit or not, but you, with your botanical knowledge, know better, I hope.
Our bananas are in crisis, you know -- a fungus is slowly wiping out the entire Cavendish monoculture upon which the contemporary banana trade is based. (More at the BBC.) An older article about this, one of the many approaching slow-motion crises which threaten our way of life, We Have No Bananas in a 2011 New Yorker, goes into detail about the seeds. Apparently Cavendish bananas are all sterile but they're looking for the occasional seed from viable bananas which can survive the fungus.
posted by Rash at 10:50 AM on March 4, 2018
posted by Rash at 10:50 AM on March 4, 2018
Some plants are far more amenable to selective breeding than others, insofar as some have much higher natural variation on which humans can act. Michael Polan makes a big deal out of this in Botany of Desire: look at the amazing variety of apples: skin color, flesh color, size, taste, moisture content, etc etc. Yet after millennia of more and less intentional breeding, nobody has yet made a tasty acorn. Likewise our modern corn is radically different from its ancestors, but avocados are still much like their ancient progenitors.
What makes some clades more mutable than others is still not well understood, but we can safely say that it is so, and the ability of some species to go polyploid definitely helps us breed desirable traits, compared to species that don't do that.
As for seedlessness on a per-fruit basis: your inclination --Seems to me a tree should either bear seedy fruit or not-- is not generally correct. The cavendish is seedless due to its triploid nature, making meiosis highly unlikely to occur.
In contrast, Clementines are seedless due to hybrid effects, and some cultivars are only seedless if they are grown in isolation from all other citrus. For that variety at least (Nadorcott), it's easy to imagine some percentage of fruit gets pollinated on sly, and hence has seeds.
Another interesting example is "seedless" watermelons, which usually have at least some easily identifiable small immature seeds, and if you buy a handful melons, you're sure to find some with a decent number of mature seeds -- it seems to just depend there on growing conditions and time of harvest.
Wikipedia has a nice article on seedless fruit which explains some of this in more detail.
posted by SaltySalticid at 10:55 AM on March 4, 2018 [7 favorites]
What makes some clades more mutable than others is still not well understood, but we can safely say that it is so, and the ability of some species to go polyploid definitely helps us breed desirable traits, compared to species that don't do that.
As for seedlessness on a per-fruit basis: your inclination --Seems to me a tree should either bear seedy fruit or not-- is not generally correct. The cavendish is seedless due to its triploid nature, making meiosis highly unlikely to occur.
In contrast, Clementines are seedless due to hybrid effects, and some cultivars are only seedless if they are grown in isolation from all other citrus. For that variety at least (Nadorcott), it's easy to imagine some percentage of fruit gets pollinated on sly, and hence has seeds.
Another interesting example is "seedless" watermelons, which usually have at least some easily identifiable small immature seeds, and if you buy a handful melons, you're sure to find some with a decent number of mature seeds -- it seems to just depend there on growing conditions and time of harvest.
Wikipedia has a nice article on seedless fruit which explains some of this in more detail.
posted by SaltySalticid at 10:55 AM on March 4, 2018 [7 favorites]
Some fifteen years ago, I peeled a banana from a hand I got at the local co-op, and at first I thought it had some terrible kind of rot, but it was actually seeds!
They were arranged in three rows that ran down the banana lengthwise, each row in one of three sections that the banana fell apart into as I peeled it. The seeds were little hard black roundish things maybe 3/16" in diameter. The rest of the bananas in the hand were normal.
I wondered at the time whether I should hold onto those seeds, but I didn't.
posted by jamjam at 11:18 AM on March 4, 2018 [2 favorites]
They were arranged in three rows that ran down the banana lengthwise, each row in one of three sections that the banana fell apart into as I peeled it. The seeds were little hard black roundish things maybe 3/16" in diameter. The rest of the bananas in the hand were normal.
I wondered at the time whether I should hold onto those seeds, but I didn't.
posted by jamjam at 11:18 AM on March 4, 2018 [2 favorites]
The little black dots in cavendish bananas are immature seeds, but they won’t develop.
posted by FencingGal at 11:33 AM on March 4, 2018 [3 favorites]
posted by FencingGal at 11:33 AM on March 4, 2018 [3 favorites]
If you search your favorite seed catalog, you can find seedless watermelon seeds.
The way it works is that you get two packets of seeds, one is the "pollinator" variety.
You grow them together, and the hybrid fruits are seedless.
posted by The Incredible Gnome at 12:02 PM on March 4, 2018 [2 favorites]
The way it works is that you get two packets of seeds, one is the "pollinator" variety.
You grow them together, and the hybrid fruits are seedless.
posted by The Incredible Gnome at 12:02 PM on March 4, 2018 [2 favorites]
Best answer: As SaltySalticid points out, breeding is some of it in regards to citrus, but depending on the variety, if the blossom that will eventually grow into a particular fruit gets pollinated with pollen from a seeded variety, seeds can form. This has resulted in ag battles in California. This WSJ article is from 2012:
The proliferation of mandarin trees, however, brought more than money. It brought a bee problem. Being seedless is a main selling point for Cuties. But if Cuties groves get cross-pollinated with pollen from seeded citrus varieties, Cuties start having seeds, too.How did the seedless ones come about? This NYT article from 2007 will give you a potted history:
As more mandarin orchards went up, more bees started to carry pollen where it wasn't welcome. In April 2006, the Resnicks' Paramount threatened to sue beekeepers for letting their bees "trespass," according to a letter sent to them and reviewed by The Wall Street Journal. Paramount declined to comment.
Irate beekeepers said that they couldn't restrict their bees' movement. A "Seedless Mandarin and Honeybee Coexistence Working Group" was convened, but it failed to reach a consensus between farmers and beekeepers.
Growers began covering their mandarin trees with nets to keep out bees. Mr. Evans started sending a helicopter over his orchards to spot beehives for removal. Scientists at the University of California helped by creating a W. Murcott tree that produced near-seedless fruit, even when visited by bees.
As growers learned starting 70 years ago with seedless grapes and more than a decade ago with seedless watermelons, shoppers will pay for convenience. To feed the demand for fruit with less mess, farmers and scientists have been chasing new varieties and developing new technologies.posted by jocelmeow at 12:26 PM on March 4, 2018 [1 favorite]
But the process began long ago, when growers found natural mutations of citrus fruits with few or no seeds, like navel oranges and Persian limes, which they propagated by grafting. A few seedless mandarins have been around for more than a century, notably the early-season satsumas, but they were limited in season and not as addictively sweet and richly flavored as the best varieties, like clementines.
Originally, clementines were seedy, and required pollination by bees to bear regular crops. In the 1960s California researchers discovered that by applying a spray at bloom, simulating the growth hormones naturally secreted by seeds, farmers could obtain good harvests of seedless clementines. Bees became undesirable.
Spanish scientists improved this technique, and in the 1980s and 1990s seedless Spanish clementines conquered markets in Europe and the eastern United States.
California growers saw this success, and in the late 1990s rushed to plant clementines, mostly in the San Joaquin Valley citrus belt, from south of Bakersfield to Fresno.
They also placed big bets on a clementine-like variety of seedless mandarin, found in Morocco in the 1980s, with the ungainly name of W. Murcott Afourer. A hybrid of Florida’s Honey Murcott tangerine, possibly with a clementine, it has thin, easily peeled skin, a deep orange color and very good flavor. Ripening after clementines, from late January to March, and producing abundantly without bees or hormones, it quickly became the hottest new citrus variety.
More terminology that gets to the core of the issue: Parthenocarpic fruit has never been fertilized, and in principle cannot make seeds. Stenospermocarpic fruit has been fertilized, and usually aborts its seeds or otherwise keeps them from developing.
So I think this means that Cavendish bananas have stenosperocarpy that is super effective, and that (some) hybrid Clementines have parthenocarpy that makes seedless fruit when unfertilized, but sets seed when fertilization occurs.
posted by SaltySalticid at 12:27 PM on March 4, 2018
So I think this means that Cavendish bananas have stenosperocarpy that is super effective, and that (some) hybrid Clementines have parthenocarpy that makes seedless fruit when unfertilized, but sets seed when fertilization occurs.
posted by SaltySalticid at 12:27 PM on March 4, 2018
It can definitely be the case that, on the very same tree, you will get some seedless fruits and some really seedy ones. This happens with my tangelo tree, which is near to a bunch of other citrus so I'm sure there's a fair amount of pollen exchange.
posted by karbonokapi at 2:15 PM on March 4, 2018 [1 favorite]
posted by karbonokapi at 2:15 PM on March 4, 2018 [1 favorite]
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