Have you ever eaten a peach with red flesh? Common people are accustomed to calling this kind of red-fleshed peach "blood peach". When cut open, the flesh and juice are as red as blood. Traditional varieties include Chinese blood peach, also called cinnabar red peach. Although red-fleshed peaches are a niche variety in the peach family, in recent years, red-fleshed peach varieties have continued to develop, and new types such as oil-blood peaches and flat-blood peaches have also been derived.
However, many people report that red-fleshed peaches with outstanding appearance do not taste that outstanding. They are more sour and some are even hard. Until now, breeders have not figured out why. Recently, the Peach Resources and Breeding Innovation Team of the Zhengzhou Fruit Research Institute of the Chinese Academy of Agricultural Sciences successfully revealed the secret. So in the future, can red-fleshed peaches achieve a win-win situation in terms of appearance and taste, and become "good-looking and delicious" peaches?
Red-fleshed peaches belong to the "small but beautiful" category in my country's peach landscape, with a total area of no more than 200,000 acres, and the production areas are mainly concentrated in Henan and Hubei. In recent years, the scale of red-fleshed peach cultivation has expanded rapidly. Wu Jinlong, a member of the Peach Resources and Breeding Innovation Team of the Zhengzhou Fruit Research Institute of the Chinese Academy of Agricultural Sciences, said that this is due to the biggest highlight of red-fleshed peaches - good nutrition.
Wu Jinlong: The red color of the pulp comes from anthocyanins, commonly known as anthocyanins, which can resist oxidation, scavenge free radicals, and help protect cardiovascular and vision. According to dietary guidelines, a daily intake of 50 milligrams of anthocyanins is beneficial to health. The anthocyanins content of red-meat peaches is more than ten times that of ordinary peaches. Eating two is basically enough. But the problem is also prominent. Many red-fleshed peaches look bright red, but when you take a bite, they are sour and astringent. Some are too hard or too ripe to be eaten. Therefore, there has always been a saying in the industry that "they look good but they don't taste good."
For decades, breeders have continued to improve red-fleshed peach varieties, but the sourness problem has not been solved. Wu Jinlong's team crossed two red-fleshed peach varieties and cultivated more than 150 offspring. They measured the pigment content, astringent substance content and acidity of the fruits for two consecutive years from 2021 to 2022. The results found that the color, astringency and acidity of red-fleshed peaches are always "bundled". The redder the color, the stronger the sour and astringent taste.
Wu Jinlong: The results of the two years consistently indicate that it is mainly controlled by genetic material and not caused by the cultivation climate. Looking further for the location, the genetic regions that control these three things happen to be squeezed into the same small section of chromosome No. 5 of the peach. This means that when breeders select individual plants with "red enough flesh" in the field, they will almost certainly bring in the astringency and sourness next to them. Relying on traditional phenotypic selection by looking, tasting, and testing is impossible to unpack.
The team further studied chromosome 5 and discovered two key genes that control the astringent and sour taste of red-fleshed peaches. The first is a gene called PpBL. Wu Jinlong said that this gene can be understood as a "master switch." It is very diligent. One hand is responsible for the synthesis of pigments that make peaches red, and the other hand is responsible for the synthesis of substances that make peaches astringent. It is like a switch that can press several buttons at the same time, directly activating three downstream genes. One is responsible for processing pigments more stably, and the other two are specialized in producing astringent substances. So as long as this gene is active, the red color and astringency will come up at the same time. "When the red meat comes out, the astringency will follow." This is the root cause of the astringency.
The other one is PpTST1, the main gene that controls acidity. In many experiments, the team turned off or strengthened the "master switch" PpBL gene, and the acidity did not change, indicating that there is no relationship between the two genes as one directs the other. So, why are the two genes so tightly bound that they cannot be shaken off? The real reason is that they live too close on the chromosomes, like two neighbors tied on a rope, always "advancing and retreating at the same time" during inheritance. Therefore, the sourness of red-fleshed peaches is not due to meddling genes, but because they are too close to each other and cannot be easily shaken off.
In order to find out the key genes that control the sourness of red-fleshed peaches, the team spent several years, step by step, selecting the two that really work from hundreds of candidate genes, and clarified the two easily confused reasons of "one gene does two things" and "two genes live close to each other". This is also a core issue that has not been clarified in the past.
Now that we have found the "key" to control the sour taste of red-fleshed peaches, is there any way to improve it? Wu Jinlong’s answer is yes.
Let’s talk about how to solve the astringency first. The key to the problem is that one gene controls both redness and astringency. The solution is to "finely tune" it, retaining only the red half of the gene and weakening the astringent half. For example, the switch area of the product is precisely modified to make it "only red and less astringent" to achieve a red color without astringency.
Let’s talk about the sour taste. The problem is that the genes that control redness and astringency are too close to the genes that control acidity and are bundled together during inheritance. The solution is to "unbundle" them: on the one hand, use molecular marker-assisted breeding to specifically screen for those rare individuals that happen to be exchanged to separate the two in a large number of offspring; on the other hand, use new gene editing technologies to directly break the bundle. This road is more difficult, but the direction is clear. In the past, breeding relied on luck, but now that there is a clear genetic roadmap and molecular markers, plans can be designed purposefully. Red-fleshed peaches that are both beautiful and delicious are definitely worth looking forward to.
Not only that, Wu Jinlong also said that the ideas proposed in this study have reference value for the quality breeding of other fruit trees and even other crops, and provide a set of useful tools for breeding. We not only found the genes, but also divided the favorable and unfavorable gene combinations into several types and made molecular markers that can be directly detected in the laboratory. In the future, breeders will be able to judge which plant will be red and delicious in the future during the seedling stage. They will not have to wait three to five years for fruiting before selecting, and the efficiency will be greatly improved. The natural pigment content of red-fleshed peaches is more than ten times that of ordinary peaches. It is a functional fruit. Making it delicious can allow more people to truly eat these beneficial ingredients.
The future of “good-looking and delicious” red-fleshed peaches is promising!
