The king of summer! Do you know some interesting facts about watermelon?

"Withered vines, old trees, and crows, there are fish and shrimps for dinner, air conditioning, WiFi, and watermelon." The happiness of summer is brought by watermelon - a piece of icy watermelon is enough to soothe a day's fatigue.

Come on, is this the scene in your dream? @鱼山饭宽

Watermelon is known as the "king of summer". It is refreshing and thirst-quenching, sweet and juicy. Watermelon contains a lot of glucose, malic acid, and rich vitamin C, and does not contain fat and cholesterol. Watermelon lovers are ecstatic! Recently, I saw a news report that a melon farmer in Shandong grew a 90-jin watermelon! 90 jin, this is not a small head, it is almost as heavy as the author. How can he grow such a big watermelon? Is this an accidental event or can it be replicated? With the development of technology, can humans grow fruits of customized sizes? Hey, why not move a small stool and eat this "melon" with me!

Image source: Veer Gallery

Part 1

Why do watermelons bear fruit?

First of all, the diversification of fruit types and shapes is the result of natural selection or artificial domestication. The reason why we have a dazzling array of various fruits is just a by-product of the plants' reproduction and survival.

In the process of evolution, plants have many tricks to spread their seeds better: for example, they spread with the help of wind like dandelions, spread by clinging to animals (fur) like cocklebur, spread by water like coconuts and water lilies, spread by their own catapulting power like impatiens and pods, and another type is to grow a layer of delicious and juicy pulp on the outer skin of the seeds like watermelons, so that after animals or people eat the pulp, the seeds (that is, watermelon seeds) become "waste" and reproduce and open up new territories for plants elsewhere. It seems that in order to survive and reproduce, plants have used various tricks, and watermelons have chosen to wrap seeds with delicious pulp.

Fruit diversity (He Chaoying et al.: The origin and evolutionary developmental mechanism of fruit diversity)

Part 2

After encountering the greedy humans, the watermelon rolled up!

After encountering humans, agronomic traits such as fruit size, taste, and sweetness began to be "directly cultivated", and plant breeders also came up with various ways to improve watermelons.

The traditional breeding method is to select parents with excellent traits from a large number of parents, perform hybridization, and then plant them in the field to select offspring that have the excellent traits of both parents. The breeding goals include high yield, high quality, resistance to pests and diseases, stress resistance, few seeds, good appearance, and storage and transportation resistance. However, this method is somewhat of a gamble, because it is more effective for quality traits controlled by a small number of genes, but it is difficult to integrate various traits controlled by multiple genes, such as high quality, high yield, and resistance.

Domestication history of two species of Cucurbitaceae (Xu Yongyang et al., Nature Genetics)

In 1953, Watson and Crick built a double helix model of deoxyribonucleic acid (DNA), opening the door to molecular genetics, which has become an important cornerstone of modern fruit breeding and ushered in the era of molecular breeding. The shape, structure, function, and size of all organisms on Earth are controlled by a set of genetic codes, which are the result of their adaptation to the environment during the long-term evolution process, and watermelon is of course no exception.

Molecular breeding is the process of integrating several or even dozens of genes associated with specific traits into the same variety through molecular markers, genetic modification, molecular design and other means to make "customized" varieties, such as low-temperature resistance, high-temperature resistance, high disease resistance, crack resistance, etc., including the size of the watermelon.

Some watermelon varieties (China Agriculture Network)

Part 3

If you want watermelon to grow well, water and light are essential.

Of course, in addition to genetic genes, there is another very important factor that affects the size of watermelons: environmental conditions, including timely and appropriate light, water, nutrient conditions, etc. If genetic genes determine the upper limit of watermelon size, then its growth environment and nutritional conditions can determine to what extent it can approach or even exceed this upper limit. This is similar to the height of a person: if the parents are tall, the children will most likely grow tall, but if the parents are not tall, children with good nutrition and enough exercise can also exceed the genetic height of their parents and grow tall.

Generally speaking, the watermelons commonly seen on the market are small and weigh one or two kilograms, while the large ones weigh 10 to 20 kilograms. This shows that the melon farmer in the news has really grasped the environmental conditions for the growth of watermelons and cultivated super-large melons using ordinary large melon varieties, and they are also delicious.

Currently, the largest watermelon in the Guinness World Records is a 316-pound giant produced in Nashville, USA. Although it is relatively large, the flesh is hollow and particularly rough, not the common water red color, and the flesh is white and tastes not good. It tastes not as delicious as ordinary watermelons. The reason may be that the nitrogen nutrition is relatively rich during the growth period, which accelerates the speed of fruit expansion, but potassium is relatively lacking, which is not conducive to the accumulation of sugar. The smallest watermelon in the world is called "Pepquinos", also known as "thumb watermelon". It is only 3 cm long and 2 cm in diameter. It is a wild plant from South America. In 1987, a Dutch company began to grow it in the United States and Asia, but in fact, it just looks like a distant relative of watermelon (watermelon is a genus of Cucurbitaceae, and thumb watermelon is a genus of Cucurbitaceae).

The cutest size difference (Sina News, Rednet)

At present, we are still in the initial stage of watermelon map construction, labeling and positioning of important traits and genes, gene mining and isolation, and genetic transformation of important genes. However, with the availability of genome sequences, functional genomic tools, and the growing knowledge of genes that control fruit development, people will be able to improve crop varieties more quickly and accurately, and achieve "advanced customization". When that day comes, dreams like riding a watermelon boat or a watermelon hot air balloon may really come true!

Produced by: Science Popularization China

Author: Yin Chunmei (Institute of Subtropical Agriculture Ecology, Chinese Academy of Sciences)

Producer: China Science Expo

The article only represents the author's views and does not represent the position of China Science Expo

This article was first published in China Science Expo (kepubolan)

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