"Tangerines in Huainan" Japanese scientists conduct genetic analysis on Chinese citrus fruits

• Citrus fruits have important commercial value, but how their diversity arises has always been a mystery

• Researchers analyzed the genomes of East Asian species and found a second diversity center in the Ryukyu Islands.
  The first previously known diversity center is located in the mountainous area of ​​southern China.
  

• They discovered a new citrus variety, native to Okinawa, which appeared when the Ryukyu Islands separated from the Asian continent about 2 million years ago.
  

• Other citrus from Okinawa and mainland Japan, including Okinawa shiikuwasha and tachibana, are hybrids of this newly discovered wild species and different species from the Asian continent.
  

• This research may have commercial significance and opens up the potential to create other hybrids with favorable traits

Citrus fruits are popular all over the world for their delicious and healthy characteristics
.
In Japan, small shiikuwasha and decorative tachibana have special cultural and historical significance

In a new study published in the journal Nature Communications, scientists from the Okinawa Graduate School of Science and Technology (OIST) and collaborators from other institutes analyzed 69 genomes from the mandarin family in East Asia and their presence in Asia Relatives on the mainland reveal a wide range of isolation, long-distance travel and hybridization
.

The story begins in Hunan Province in southern China, which is the center of wild citrus diversity and the most famous genetic source of citrus
.
When the scientists reanalyzed the previously published genome data, they unexpectedly discovered that the wild oranges in this mountainous area were divided into two subspecies

Dr.
Guohong Albert Wu, a research collaborator at the Lawrence Berkeley National Laboratory in California, said: "We found that one of these citrus subspecies can produce offspring with the same genes as the mother
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Like many other plants, wild Citrus is usually reproduced when the father’s pollen is combined with the mother’s egg, and the seeds are mixed with genes from both parents

Back in Okinawa, the researchers took a closer look at a strange shiikuwasha-like citrus.

It is worth noting that the researchers found that all shiikuwasha are hybrids of a very specific type-one parent is from the local Ryukyu species (Ryukyu), and the other is from the Asian continent
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Surprisingly, all shiikuwasha have the same mainland mandarin parents, which means that all shiikuwasha are half brothers and sisters

They concluded that tens of thousands of years ago, officials on the Asian continent were transported to the land that would later become the Ryukyu Islands through human or natural means
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There it mates with local Ryukyu citrus

Therefore, all shiikuwasha varieties found in the Okinawa market today are the offspring of this mating and are reproduced asexually so that stable varieties like golden shiikuwasha can be passed down from generation to generation
.

So what about tachibana and other East Asian mandarins?

Dr.
Chikatoshi Sugimoto, postdoctoral fellow in molecular genetics at OIST, explained: “They are all hybrids! The lineage of tachibana also seems to originate from the newly discovered Ryukyu species and another mandarin from China, but its birthplace may be present in mainland Japan.

.
"

Not only did they discover the genetic patterns of shikuwasha and tachibana, the researchers also discovered another half-brother family, including various traditional Ryukyu varieties-oto, kabuchii, tarogayo, and other unnamed citrus genera
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This family is now called "yukunibu" (sour citrus in the local Okinawa language) by researchers and is much younger than shikuwasha and tachibana

Professor Dan Rokhsar, the lead researcher of the OIST Molecular Genetics Department, concluded: "It is interesting to unravel the story of citrus diversification and its relationship to the biogeography of the region
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But it may also have commercial value
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There are others.
Are there possible types of hybrids? Can we create new hybrids that are more resistant to disease or drought, or have other desirable characteristics? By looking back at the past, we can create various possibilities for the future
.
"

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Original search: 10.
1038/s41467-021-24653-0