The copyright of the original article belongs to the WeChat public account
"Bring science home" all
Guangzhou
The "crispy honey" variety grown in the Conghua orchard (Image source: Nanfang Daily)
Written by | Quasimodo by the river
Proofreading | Ah Xian
In 1100 AD, Su Shi was pardoned by the imperial court and returned to the mainland from Hainan.
As a famous "foodie", even though his life was bumpy, Su Dongpo ate wherever he went, leaving a lot of literary works about food. Among them, when he was demoted to Huizhou, Guangdong, he left the famous poem of "eating 300 lychees a day, and being a Lingnan person for a long time", and became the most famous lychee "delivery expert" in history.
Friendly reminder, although lychee is delicious, you can't eat too much, otherwise you may suffer from "lychee disease" (Image source: theferns.info)
This time back to the mainland, Su Shi's first stop was Hepu in Guangxi. At that time, it was already the seventh month of the lunar calendar, and lychee (Litchi chinensis) had already been taken off the market. Even if Su Dongpo thought about it, he couldn't taste the taste of lychee again.
However, it is gratifying that Su Dongpo ushered in the ripening season of longan (Dimocarpus longan).
Because the fruit is peeled and crystal clear, and the black-red core is faintly visible, it is very similar to an eyeball, so it is named "longan", which is a common fruit in mainland China and Southeast Asia (Image source: foodnext.net)
Gourmand Su Shi went online again, and after eating a full meal of longan, he also left a poem called "Lianzhou Longan Tastes Extremely Delicious and Rivals Lychee" (to the effect that Lianzhou's longan tastes delicious and can be compared to lychee):
"Longan and lychee are different from the same father. If you are sweet and orange, it is not easy to get along. ”
The gist of the poem is that longan and lychee are actually two different branches of fruit belonging to the same category. Just like citrus and oranges, it is difficult to distinguish from the outside, or to make judgments about high and low.
It can be said that Su Shi is not only a gourmet, but also a careful naturalist, who has keenly discovered the similarities and differences between longan and lychee. In today's plant classification, it is also proved that the two belong to the same family, and they are both plants of the Sapindaceae family.
In addition to the lychee and longan that everyone is familiar with, there are also rambutan (upper right), grape mulberry (lower left), honeyberry (lower right) and other uncommon fruits in the soapberry family, and the soapberry family is also a resource library with great potential for fruit development (honeyberry picture source: Tang Jingwei @PPBC, the rest of the picture source network)
However, what Su Dongpo never imagined was that after a thousand years, scientists successfully crossed lychee and longan. This fruit, which combines the sweetness of lychee with the refreshing longan, is ready to be put on the table.
It is very difficult to get these two species to cross naturally in nature – they are two separate species, after all. However, there is indeed another plant in the soapberry family, just like a "suture monster", and the fruit grows very much in line with the characteristics of the combination of lychee and longan, and the ancient people in the mainland named it Dimocarpus confinis.
Longli fruit has the characteristics of both lychee and longan (Image source: Huang Jianghua @PPBC)
Because the longan fruit is often used as a traditional medicinal material after drying, and the longan is very suitable as a rootstock for longan grafting, it was once widely cultivated in the Guangxi region of the mainland. Its fruit has also been passed off as longan, but because the fruit of Longli is poisonous, it is not suitable for consumption.
Even in an ancient TV series "Kangxi Weifu Private Interview 2", there was a scene where Long Li was used to pretend to be longan.
The stills from the play "Kangxi Weifu Private Interview 2", there is a story in it that uses Long Li to pretend to be longan (Image source: YouTube.com)
At one point, botanists suspected that the dragon lily was the result of a natural hybrid between lychee and longan. However, after the gene sequencing, the truth was revealed: the homology of Longli was lower than that of Longan and Lychee, and it was the first to evolve and separate before the two. To put it in layman's terms: Long Li is not the "child" of the two, but the "uncle" of lychee and longan.
The basic condition for speciation is that there are obvious reproductive barriers with other species, and species will also use various means to limit communication with other species. This is the basis for a species to ensure its own genetic continuity, but for scientists, it has become a "roadblock" for breeding new varieties.
The homology between Longan and Rambutan was higher but lower than that between Longan and Lychee (Photo source: Fujian Journal of Agricultural Sciences doi: 10.19303/j.issn.1008-0384.2019.01.006)
The same is true for the hybridization of lychee and longan. Because they are species of different genera, according to genetic sequencing, they began to diverge about 10 million years ago. Trying to make them "the crystallization of love" is no less difficult than cultivating hybrid rice, and there are at least three huge difficulties waiting to be solved.
First of all, it is necessary to find out the "family tree" of lychee and longan. In order to cross two species, the most basic condition is to know enough about the parents. Although both are common fruits, research on them started late because they are tropical plants and have a small distribution area on the continent. Other countries have limited research on the two, and even the number of chromosomes in the somatic cells of these two plants is not clear.
There is a saying in the fruit industry that "the world's lychees look at China, and China's lychees look at Guangdong", with an average of one out of every three lychees produced in Guangdong (Image source: newsgd.com)
With the efforts of scientists, around 2010, the mainland constructed the molecular genetic map of lychee and longan, and theoretically confirmed the possibility of hybridization between the two.
The next challenge is to choose the right breed for crossbreeding. The mainland is the world's largest producer of lychee and longan, accounting for about 70% and 60% of the world's production, respectively. Especially lychee, there are many varieties formed on the mainland since ancient times. Cinnamon flavor, glutinous rice balls, concubine smile...... These are all familiar breeds. But this also brings "sweet trouble" to scientists, which varieties are suitable for crossbreeding?
There are many varieties of lychee, and behind it are the dedication and dedication of countless fruit farmers and agricultural scholars (Image source: pdnews.cn)
After more than ten years of experiments, scientists in the mainland chose Shi Kip longan as the female parent and Ziniang Xi Lychee as the paternal parent. Shi Kip longan can be called the most delicious longan variety in the mainland, and the yield is also considerable, but there is a fatal shortcoming that the fruit is relatively small, and Ziniang Xi Lychee has a more resounding name: Lychee King. It doesn't have that sweet taste and a slightly sour taste, but its fruit is large, even more than the size of an egg, and it has a high yield.
After a long selection, these two varieties were finally chosen, not only because of their distinctive characteristics, the advantages and disadvantages of the hybridization can form a perfect complementarity, but also because Zi Niangxi is a late-maturing variety, and the flowering period is shorter than that of Shi Kip longan, which can provide more energetic pollen.
Crispy honey and its parent varieties (Image source: South China Agricultural University)
However, even so, in order to achieve hybridization between the two, there is a third problem: the lack of a corresponding identification mechanism between the hybrid parents, and the longan cannot recognize the information of lychee under normal circumstances.
Huanong's team used a technique called "male-pollination," a combination of physical, chemical and biological methods that allowed longan to identify the pollen of lychees and produce fertilizers.
Guided pollination is the most difficult part of the hybridization process, and because the pollen of lychees is very small, the pollination work is like carving on rice (Image: South China Agricultural University)
After 15 years of unremitting efforts after continuous hybridization and screening. In 2022, in Conghua, Guangzhou, the variety of crispy honey hybridized by longan and lychee was officially unveiled.
Its peel is yellowish-green in color, similar to longan, but with lychee-like lobes on it. The crisp honey flesh is completely free of residue, and the sugar content is as high as 20%-24%.
Comparing the crispy honey with the parent stone kip, it can be seen that the peel of the crispy honey is cracked obviously (Image source: South China Agricultural University)
According to those who tasted it at the scene, "When the skin is peeled off, the inner flesh is full and contains a lot of water. With each bite, the crisp sound echoes in the mouth, making people have an endless aftertaste. And the crispy honey flesh is delicate, the taste is very tender, and it is very enjoyable to chew. ”
Crystal clear crisp honey pulp (Image source: South China Agricultural University)
In addition to its unique appearance and taste, the hybridization also brings many advantages to Crispy Honey, such as growing much faster than ordinary longan trees, ripening later than normal Silk Kip, which allows for staggered peak listing, and especially cold hardiness, which far exceeds that of its parents, which means that the growing area of Crispy Honey can spread northward.
Due to the existence of "partial maternal inheritance" in the plant kingdom, that is, the traits of hybrid offspring are more similar to those of the female parent, so the current identity of brittle honey is the variety of longan. But since brittle honey can produce stable and fertile seeds, we may be able to discuss whether it is a new species.
Liu Chengming, head of the crisp honey breeding team and professor of South China Agricultural University (Image source: Nanfeng Window)
The appearance of crispy honey is only the beginning of the cross-genus hybridization of longan and lychee. Huanong's team is not only experimenting with more hybrid possibilities, but also cultivating seedless hybrids.
Imagine: a fruit with the dual flavors of lychee and longan, without having to spit out the pit, this is simply the most anticipated moment of summer.
Happiness unique to summer (Image source: South Wind Window)
According to reports, in 2023, crispy honey has been promoted in some areas of Guangzhou through customized sales, and it is expected to be fully launched in 2025.
This is also where we are luckier than Su Shi today: we feel the history of the past and witness the arrival of the future.
I don't know what kind of work Su Dongpo would create if he lived today, after tasting crispy honey (Image source: Tiangong AI generation)
Resources:
[1] Gezhi Pulpit. Sweet longan and lychee "married"? This family affair made my tears flow from the corners of my mouth|Liu Chengming.https://mp.weixin.qq.com/s/rVJfgbLi3PGtOAK_94lRAQ
[2] Nanfeng Window.Longan × Lychee = The first new hybrid variety of Longan Lychee was born.https://mp.weixin.qq.com/s/-S6tl_SfpkkUPVUgOuMnuA
[3] Liu Chengming, Hu Youli, Fu Jiaxin.Research progress on the application of biotechnology in litchi longan propagation and variety improvement[J].South China Fruit Tree, 2003, 32(6):5.
[4] Yuhui Zhao, Youli Hu, Yinshan Guo, Jia Zhou, Jiaxin Fu, Chengming Liu*, Jiang Zhu, Mingjun Zhang, Acquisition and molecular identification of distantly related hybrids between litchi and longan, Acta Fruit Sinica, 2008, 25(6): 950-952
[5] Zhang Yongfu, Lu Bobin, Wang Ying, Pan Lijia, Hu Youli, Zhou Jia, Zhao Haiyan, Liu Chengming (corresponding author), Chromosome observation of some rare germplasm of litchi and longan, Acta Horticulturae Sinica, 2010, 37 (12): 1991~1994
[6] Jiang Fan, Chen Xiuping, Zheng Shaoquan.Phylogeny of Longli based on the ITS sequence of Sapindaceae[J].Fujian Journal of Agricultural Sciences, 2019, 34(1):5.
[7] Guangzhou Radio and Television Station. "Crispy honey" is finally here! Guangzhou midsummer fruits, "seamless" on the new →.https://mp.weixin.qq.com/s/JbZT9_6XID9AJjqafBrVhQ