Author Topic: The Citrus Family Tree  (Read 2137 times)

A.T. Hagan

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The Citrus Family Tree
« on: October 30, 2017, 12:54:18 PM »
https://www.nationalgeographic.com/magazine/2017/02/explore-food-citrus-genetics/

All the oranges, lemons, limes, and grapefruits you’ve ever eaten are descendants from just a few ancient species.
By Daniel Stone



*Researchers continue to debate whether kumquats are indeed in the Citrus genus.
**Most “pure” mandarins have a small proportion of pomelo genes.


Quote
Citrus, in many ways, stands alone. So many cultivated species have come from so few primary ancestors. Just three, in fact: citrons, pomelos, and mandarins, all native to South and East Asia before they started their journeys west, to places like Florida, California, and Brazil that built entire economies around fruits from the other side of the world.

Such simple lineage is the result of impressive commonality. Almost all citrus has the rare genetic combination of being sexually compatible and highly prone to mutation. Such traits allow their genes to mix, for thousands of years on their own, and eventually, at the hands of humans. The product of so much natural crossing in the wild and selective breeding at research farms and in fields is every orange, lemon, lime, and grapefruit you’ve ever eaten.

No other fruit genus can boast such pedigree, and new research is bringing clarity to the origin of citrus. Grapefruits are a human discovery, less than 300 years old. But citrus itself is ancient. Fossilized leaves discovered in China’s Yunnan Province in 2009 and 2011 suggest citrus has existed since the late Miocene epoch, as many as seven million years ago. Humans, however, have brought a great winnowing: Out of thousands of wild types, only a few dozen have become commercial behemoths like the navel orange, Eureka lemon, and Mexican lime. They’re the citrus one percent.

The scientists who study citrus love it for its appeal, its mystery, and its drama. “There’s something fascinating, freaky, even sexy about citrus,” says pomologist David Karp, whose research informs the above illustration. A bacterial disease called huanglongbing (a.k.a. citrus greening) that causes plants to defoliate, decay, and eventually die, is threatening commercial production on every arable continent, including North America, where the disease arrived in 2005.

Yet a fruit group of such illustrious history won't be exterminated so easily. The future is likely to bring more types of citrus, not fewer. “Citrus is competitive,” says citrus breeder and geneticist Fred Gmitter, explaining how global researchers race to develop, say, mandarin oranges that are sweeter, seedless, and easier to peel. “In the near future you’ll see a lot of outside-the-box new stuff.” And, an ever expanding family tree.

Daniel Stone is an editor for National Geographic magazine, where he covers science, technology, and agriculture. His book, The Food Explorer, on the life and adventures of food spy David Fairchild, will be published by Dutton (Penguin Random House) in 2018.


SoCal2warm

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Re: The Citrus Family Tree
« Reply #1 on: May 07, 2019, 07:51:45 PM »

Millet

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Re: The Citrus Family Tree
« Reply #2 on: May 07, 2019, 10:46:20 PM »
It is stated that the citron, pummelo and mandarin are the three "primary" fruits, and all other citrus varieties ever produced are some combination of these three primary fruits.  My question:  the three primary fruits are all citrus.   How is it that mother nature in the beginning, over 7 million years ago, develop three separate and  unique fruits and all three are in the same family of citrus?  They must have developed from some other preexistent plant so that all three fruits came into existence in a same biological family.
« Last Edit: May 07, 2019, 10:57:39 PM by Millet »

SoCal2warm

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Re: The Citrus Family Tree
« Reply #3 on: May 07, 2019, 10:58:30 PM »
My question:  the three primary fruits are all citrus.   How is it that mother nature in the beginning, over 7 million years ago, develop three separate and  unique fruits and all three are in the same family of citrus?

Well, obviously if you believe the theory of evolution, all citrus species originally descended from a common ancester. As the species spread about to different geographical regions, the gene pool began to gradually diverge as it adapted to local conditions.

Ever wondered why pomelo rinds are so thick? The likely reason is because the trees, as they grow in the wild (not on grafted rootstock) can get quite tall, maybe 45 feet high, and so the thick rind cushions the impact when the big heavy fruits fall.

The different citrus families are a good example of the blurry line that can exist between species and subspecies.
The general consensus among taxonomists are that they constitute separate species (even though it is obviously possible for them to interbreed). It's a similar story for different families of cherry, or roses.

Sylvain

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Re: The Citrus Family Tree
« Reply #4 on: May 08, 2019, 09:30:32 AM »
To be more serious, this is only about cultivated citrus!.
The cultivated germplasms are very small part of the genetic resource compared to wild citrus.
This theory of four parents can only explain cultivated citrus not wild citrus.

We must be very cautious about all those 'trees'. No use to speak of Tanaka and swingle classifications...  ;)
The modern genetic classifications are breaking everything we were believing in. An example is the papeda family which was centered on Ichang papeda and has been proved completely wrong!

SoCal2warm

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Re: The Citrus Family Tree
« Reply #5 on: May 08, 2019, 11:17:06 AM »
It is stated that the citron, pummelo and mandarin are the three "primary" fruits, and all other citrus varieties ever produced are some combination of these three primary fruits.
That's basically true, but not entirely completely true.
A few of the cultivated citrus have important ancestry from other original citrus species as well.
For example, lime comes from C. micrantha, kaffir lime comes from C. latipes (Khasi papeda), Yuzu is believed to have ancestry from C. ichangensis (or if not that, is closely related to it). Shikuwasa in Japan and Taiwan has ancestry from C. tachibana, a native original species to the islands that appears to be a closely related but distinct subspecies to mandarin.
Then you also have kumquat, which gave rise to calamondin.
Those are pretty much all the main exceptions, off the top of my head.


An example is the papeda family which was centered on Ichang papeda and has been proved completely wrong!
I believe all the papeda species are closely related. Or is that not true?

manfromyard

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Re: The Citrus Family Tree
« Reply #6 on: May 08, 2019, 12:32:03 PM »
To be more serious, this is only about cultivated citrus!.
The cultivated germplasms are very small part of the genetic resource compared to wild citrus.
This theory of four parents can only explain cultivated citrus not wild citrus.

We must be very cautious about all those 'trees'. No use to speak of Tanaka and swingle classifications...  ;)
The modern genetic classifications are breaking everything we were believing in. An example is the papeda family which was centered on Ichang papeda and has been proved completely wrong!
True, indeed. In this article there is no mention of trifoliate citrus or kumquats. So the wild forms are not accounted for here.

Sylvain

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Re: The Citrus Family Tree
« Reply #7 on: May 09, 2019, 08:14:36 AM »
> I believe all the papeda species are closely related. Or is that not true?
Not true. It even is the opposite. Papeda group is  a catch-all for all large winged petiole citrus.

«The Papeda group includes citrus from different geographical origins; Citrus micrantha could be native to the southern islands of the Philippines, C. latipes to north-east India, C. macroptera near to New Caledonia, C. celebica to the Indonesian islands, and C. hystrix, of an uncertain origin, could be from the Philippines.»

And now the Honghe papeda from Yunnan (China). The genetic analyzes place it far from the ichang papeda and close to the kumquats !!!