Cabbage, also known as "Song" in ancient times. In a winter of a certain year in the Tang Dynasty, heavy snow fell heavily, and Meng Jiao and Lu Tong visited Han Yu. Han Yu shredded the cabbage and stewed it slowly, paired with newly dug winter bamboo shoots. When people taste pine and bamboo shoots, boil wine and discuss poetry, there is a saying that goes' late pine finely cuts fat beef tripe, new bamboo shoots taste tender horse hooves for the first time '. Nowadays, as a subspecies of Chinese cabbage, Chinese cabbage has become the largest winter stored vegetable in northern China. The annual sowing area of Chinese cabbage is about 27 million mu, accounting for about 14.4% of the total vegetable sowing area in the country. In recent years, people's demand for Chinese cabbage has become increasingly diversified. However, due to limited intra species genetic resources, relying solely on intra species hybridization is no longer sufficient to meet market demand. Utilizing the excellent genetic resources of other species for cross species hybridization is also constrained by reproductive isolation. The research team led by Duan Qiaohong, Dean of the School of Horticultural Science and Engineering at Shandong Agricultural University, has broken through the reproductive isolation barrier of distant hybridization and successfully obtained inter species and inter genus distant hybridization embryos of Chinese cabbage, opening up new ideas and approaches for distant hybridization breeding and providing more possibilities for future vegetable breeding. The relevant research results were previously published in the international journal Nature and selected for the "2024 Major Advances in Chinese Agricultural Science" published by the Chinese Academy of Agricultural Sciences. Hybrid breeding can produce excellent varieties of Chinese cabbage, which is one of the vegetables with the largest cultivation area and highest yield in China, and occupies an important position in the vegetable market. In the past, as a typical winter storage vegetable, the supply period of Chinese cabbage was mostly limited to winter. With the development of modern agricultural technology, China has not only achieved annual supply of Chinese cabbage, but also cultivated improved varieties rich in various nutrients. Of particular note is that with the continuous breakthroughs in new breeding technologies, Chinese cabbage varieties have significantly improved their ability to resist pests and diseases compared to traditional varieties, while maintaining excellent taste. Distant hybridization breeding is one of the very important breeding techniques for cruciferous vegetables such as Chinese cabbage. Duan Qiaohong explained: "Distant hybridization breeding is the process of crossbreeding different species, genera, and even more closely related species, recombining the excellent traits of different species, and creating new types of variation or new species. Distant hybridization breeding can effectively broaden the genetic range of Chinese cabbage germplasm resources. Due to long-term survival and evolution in the wild, wild species possess excellent genetic resources such as disease resistance, insect resistance, and stress resistance, "said Duan Qiaohong." By introducing the excellent resistance genes of wild species into the genome of vegetable cultivars through distant hybridization, it is expected to improve the resistance of vegetables to pests and diseases, and ensure vegetable production and food safety. "In fact, distant hybridization breeding has been widely used in crop breeding for a long time. Li Ru, the breeding backbone of Duan Qiaohong's research team, introduced that in the 1970s, Li Zhensheng, an academician of the CAS Member, after more than 20 years of in-depth research, cultivated the distant hybrid "Xiaoyan 6" between wheat and Elytrigia elongata. Xiaoyan 6 is an important backbone parent for wheat breeding in China. Currently, it has been promoted over 300 million mu nationwide, increasing wheat production by more than 15 billion jin, "said Li Ru. Solving the problem of fertilization in Chinese cabbage: In the process of distant hybridization breeding, three common but difficult to overcome interspecific isolation phenomena are distant hybridization incompatibility, premature death or sterility of hybrids, and crazy separation of offspring. Through the unremitting efforts of researchers, China has achieved hybridization between two closely related species, Chinese cabbage and cabbage. However, hybridization with distant genetic relationships is currently difficult to achieve, "Duan Qiaohong explained. Taking European mustard as an example, it is a cruciferous plant with high resistance to pests such as diamondback moth and cabbage armyworm, and has excellent anti insect genes. However, due to the distant genetic relationship, distant hybridization between Chinese cabbage and European mustard has not yet been achieved. In order to break this dilemma, the research team led by Duan Qiaohong has been exploring the formation mechanism of distant hybridization barriers in Chinese cabbage since 2017. We found that the main reason for the obstacle of distant hybridization in Chinese cabbage is the inability to successfully fertilize, "Duan Qiaohong told reporters. At that time, the research team observed the pollination and fertilization process of Chinese cabbage and found that after distant pollen landed on the stigma of Chinese cabbage, it was difficult to hydrate, germinate and grow, seriously hindering the fertilization process. We detected that distant pollen can rapidly cause an increase in reactive oxygen species in the stigma, which suggests that reactive oxygen species may have an inhibitory effect on distant pollen, "said Duan Qiaohong. After identifying the cause, Duan Qiaohong led the team to prescribe the right medicine. By removing reactive oxygen species from the stigma, we broke the isolation of distant hybridization reproduction in Chinese cabbage and promoted the growth of distant pollen on the stigma, "said Duan Qiaohong. In this way, Chinese cabbage can freely choose" distant relatives "for" marriage ". There are still multiple technological bottlenecks that need to be overcome. Currently, distant hybridization technology has shown great potential for application in the breeding of cruciferous vegetables represented by Chinese cabbage. This technology helps to utilize the excellent genetic resources of other species to cultivate higher quality vegetable varieties Duan Qiaohong introduced that the research team has obtained distant hybrid seedlings of Chinese cabbage and cabbage, Chinese cabbage and arugula, Chinese cabbage and radish, etc., providing a rich material foundation for subsequent Chinese cabbage breeding. Technology leads, standards accompany. At present, the research team has developed three group standards in Shandong Province, including the "Technical Regulations for Pollination of Chinese Cabbage by Distant Hybridization" and the "Technical Regulations for Affinity Identification of Chinese Cabbage by Distant Hybridization", based on years of experience in distant hybridization. These standards provide technical support for relevant units to promote distant breeding of cruciferous vegetables. But in order to apply distant hybridization breeding technology on a large scale, we still have many technical bottlenecks that need to be overcome Li Ru told reporters, "Taking the distant hybridization of Chinese cabbage and European mustard as an example, although we can obtain hybrid embryos, we are still far from meeting the requirements of distant breeding." Li Ru said that the team will continue to analyze the molecular mechanism of stigma barriers in distant hybridization, develop more efficient distant hybridization pollination techniques, and further solve the problem of fertilization in distant hybridization combinations. After successful fertilization, due to distant hybridization breaking the original genetic system of Chinese cabbage, we still need to solve the problem of hybrid premature death through embryo rescue technology Li Ru said. How to improve the survival rate of distant hybrid seedlings is also the focus of the team's next research direction. As long as we obtain a hybrid variety containing exogenous excellent genes, we can transfer it to other Chinese cabbage varieties through intraspecific hybridization, achieving large-scale application Li Ru stated that the team is still deeply cultivating breeding technology and striving to achieve independent and controllable seed sources as soon as possible. Now, the biggest wish of Duan Qiaohong's team is to widely apply the achievements of distant breeding technology to the breeding and production of cruciferous vegetables such as Chinese cabbage, and achieve the transformation of scientific research results into practical productivity. (New Society)