Do you know how hard passion fruit works to be eaten by you?!

Recently, eight new passion fruit varieties developed and cultivated by the team of Wu Fuchuan, a senior laboratory technician at the Garden and Horticulture Center of the Xishuangbanna Tropical Botanical Garden of the Chinese Academy of Sciences (referred to as "Banna Botanical Garden") , have been successfully registered internationally.

This new variety registration is a re-certification following the international registration of the new passion fruit variety Xishuangbanna Red (Banna Red) in 2021, marking that the research and development capabilities of new passion fruit varieties of the Banna Botanical Garden have reached the domestic leading level.

Passion fruit, the star of the Passiflora genus: a tropical fruit that is both ornamental and edible

Most plants in the genus Passiflora are herbaceous perennial vines. There are about 500 species in the world, more than 90% of which are distributed in tropical to subtropical regions of Central and South America, and only a small number of species are distributed in Asia.

The most famous of the Passiflora genus is the Passiflora edulis Sims, which is native to South America. The fruit is ellipsoidal in appearance, shaped like an egg, with a strong juice aroma, and has the flavors of many fruits such as pineapple, strawberry, banana, guava, lemon, etc. Its English name is passion fruit, and its Chinese name is passion fruit .

Passion fruit. Copyrighted images from the gallery. Reproduction may lead to copyright disputes.

Passion fruit is a vine native to tropical America. The most unique thing about it is its flowers. Most plants in the genus Passiflora have five sepals and five petals arranged in two rounds. The flowers of plants in the genus Passiflora have a large number of whisker-like filaments, which are called " corona " in botany.

The length, curvature and color of the coronas of different types vary greatly, and are the most peculiar structure on the passion flower . They are arranged around the center of the flower, usually in 2 to 3 wheels, shaped like scales on a dial, and their erect, forked stamens and pistils shaped like pointers make the entire flower look like a clock face, which is very peculiar.

Passion fruit flowers. Copyright image. Reproduction may cause copyright disputes.

Passion fruit has not been in China for long . It was first introduced to Taiwan in the early 20th century. After the founding of New China, it was introduced from Southeast Asia to coastal provinces such as Guangdong and Fujian. It was not until the 1980s that it gradually became popular in the fruit market in South China and was promoted in Guangxi, Fujian and other provinces. Currently, there are three types of commercially cultivated passion fruit: purple fruit, yellow fruit and their hybrids.

Passion fruit is rich in nutrients, can bear fruit for a long time, and can be harvested all year round. It has extremely high economic value and has developed into a fruit widely planted in tropical and subtropical regions around the world. Passion fruit is native to tropical South America. It likes a warm environment with plenty of sunshine and water all year round. It is not frost-resistant and likes fertile soil with a pH of about 6.0 and good drainage. It is suitable for large-scale cultivation in Fujian, Guangxi, Guangdong, Hainan and Yunnan in my country.

Xishuangbanna is located in southern Yunnan, on the northern edge of the tropics. The climate and soil conditions here are very suitable for growing passion fruit. There are even wild plants growing naturally in the bushes on the roadside. The Xishuangbanna Botanical Garden has introduced and promoted the planting of passion fruit since the 1980s, and later gradually promoted it throughout Xishuangbanna. The Dai people in Xishuangbanna like to eat sour fruits and vegetables. They have long used passion fruit as a sour ingredient to make various delicacies, so passion fruit has also become an important fruit in the daily life of the local people.

Passion fruit drink. Copyright image. Reprinting may cause copyright disputes.

It is not easy to make passion fruit give birth smoothly

There are many horticultural varieties of Passionflower, and there are currently thousands of varieties around the world, but it is not easy to cultivate a unique new variety.

Wild Banna passionflower in the wild. Image source: Xishuangbanna Tropical Botanical Garden, Chinese Academy of Sciences

At present, there are two main ways to breed new passion fruit varieties: interspecific hybridization and polyploidization .

Interspecific hybridization is to pollinate two wild species (or fertile cultivars), cultivate flowering plants from the seeds obtained, and then select the offspring with excellent, unique and stable flower (or fruit) traits as new varieties. This method takes a long time and the variation of the offspring is limited.

Polyploid breeding is the process of doubling the chromosomes of diploid seedlings by physical or chemical methods to obtain tetraploid offspring. This method can usually produce new varieties with larger flowers or fruits.

When it comes to breeding new passion fruit varieties, the most critical thing is the selection of excellent parental hybrid combinations , which means that it is necessary to find the real "father and mother" for the "passion fruit baby" and give the new variety proper artificial care during its growth so that it can bloom and bear fruit smoothly, and finally select excellent varieties with unique traits.

The whole process is time-consuming and labor-intensive, taking as little as one year or as long as two years.

In addition to the difficulties in selecting parents, the planting process also faces pests and diseases including stem base rot.

Taking stem base rot as an example, in order to overcome the harm of this devastating disease to plant growth, Wu Fuchuan's team from the Gardening and Horticulture Center of the Xishuangbanna Botanical Garden creatively selected the more resistant fine-toothed passion fruit (P. serrulata) and green passion fruit (P. maliformis) as parents, and bred the hybrid offspring F1 resistant to stem base rot through artificial pollination and hybridization. They used it as rootstock, and then selected young passion fruit branches with leaf buds as scion. Finally, the two were grafted together to cultivate new passion fruit seedlings .

Resistant rootstock. Image source: Xishuangbanna Tropical Botanical Garden, Chinese Academy of Sciences

Welcome to the visual feast of passionflowers

Most plants of the genus Passiflora have very beautiful and delicate flowers with bright colors, long flowering period and vigorous growth. They are a type of tropical vine flowers with high ornamental value.

In recent years, Wu Fuchuan's team has been collecting native passion fruit species with high ornamental value and carrying out a large amount of artificial hybridization breeding work. In August 2021, the Xishuangbanna Red passion fruit cultivated by the team became the first new variety in China to be authoritatively certified by the International Passion Fruit Association, which is of great pioneering significance .

The new passion fruit variety "Banna Red". Image source: Xishuangbanna Tropical Botanical Garden, Chinese Academy of Sciences

Banna Red is a tetraploid bred by artificial mutagenesis. Compared with its diploid parent, red passion fruit (P. miniata), its petals and sepals are thicker, the edges of the petals and sepals have irregular teeth, both whorls of corona are thicker and shorter, and the flowers secrete more nectar.

The glands on the stigma, anthers, and bracts are all enlarged, the leaves are about 8.5 cm long and 5 cm wide, thicker and larger than the parent, with irregular sharp teeth on the edges. The whole flower is about 45% heavier than the parent red passionflower.

Anatomy of "Banna Red". Image source: Xishuangbanna Tropical Botanical Garden, Chinese Academy of Sciences

Two years later, eight new passion fruit varieties cultivated by the team have successfully obtained international registration certification . The eight new varieties are Ziying, Xiyuan Red, Zhuangyuan Red, Banna Sky, The Spirit of the sea, Mansai Red, Mansai1, and Mansai8.

Ziying, Xiyuanhong, Zhuangyuanhong, and Banna sky. Image source: Xishuangbanna Tropical Botanical Garden, Chinese Academy of Sciences

Sea Elf, Mansai Red, Mansai Red No. 1, Mansai Red No. 8. Image source: Xishuangbanna Tropical Botanical Garden, Chinese Academy of Sciences

The most noteworthy of these is the purple passion fruit , which is an excellent offspring selected from the F1 offspring obtained by cross-pollination of the fine-toothed passion fruit and the green-fruited passion fruit. The appearance of the flower is similar to that of the mother green-fruited passion fruit, but the fruit is yellow when ripe and has a strong aroma. It can be used as a grafted rootstock for cultivating commercial passion fruit seedlings, and it is also a new variety of passion fruit that is both ornamental and edible. It is very worthy of promotion and planting in production .

Xiyuanhong, Zhuangyuanhong, Mansaihong, Mansai No. 1 and Mansai No. 8 are all hybrid offspring of red passionflower. The flowers are all mainly rich red in color. The main differences lie in the length and width of the petals, as well as the color and length of the corona.

The main feature of Xiyuanhong is that its petals are folded downwards; Zhuangyuanhong has yellow-green leaves; Mansaihong has a darker color, dark red, and the corona is mainly white; Mansai No. 1 and Mansai No. 8 are quite similar, but the former has a red and white corona, while the latter has a dark black corona.

The three new passion fruit varieties are named "Mansai" because they were all selected and bred from the fruit picking garden jointly built by the Xishuangbanna Botanical Garden and Mansai Village, Menglun Town .

Can ornamental plants also have an “identity card”?

There are many kinds of ornamental plants in the world, and there are also many varieties cultivated artificially. The diversity of species and varieties has reached a very complex level. If there is no strict international standard management system as a basis and criterion to constrain, the circulation of various ornamental plant varieties will become chaotic. Therefore, it is very necessary to carry out international registration work in the field of ornamental plants in the world.

The international registration of ornamental plant varieties is a system in the horticultural academic community, which is of great significance to ensure the consistency, accuracy and stability of the names of ornamental plant varieties . Usually, a new flower variety must be reviewed and confirmed by the corresponding international registration agency before its name can be registered in the annual report.

This is very similar to the ID card registration in human society. Once a new plant variety has such an "ID card", it is equivalent to obtaining recognition from the international horticultural system, establishing a standard name and file for the variety, which will facilitate future research, production, promotion and circulation.

International registration certificate for "Banna Red". Image source: Xishuangbanna Tropical Botanical Garden, Chinese Academy of Sciences

At present, the international registration agency for new varieties of Passiflora is the Passiflora Society International in the UK. Applicants can directly fill in relevant information on the official website of the agency to register the variety. Applicants are required to provide personal information, climatic conditions of the breeding site, characteristics of the flowers, leaves and fruits of the new variety, and relevant color photos.

Conclusion

Although the process of breeding new plant varieties is difficult, it can have a profound impact on an industry. More new varieties of flowers and fruits will provide more choices for humans, increase variety diversity, and avoid serious consequences caused by heavy losses in the production of a single variety.

Young plant sprouts growing. Copyright image from the photo library. Reproduction and use may lead to copyright disputes.

Wu Fuchuan's team at the Garden and Horticulture Center of the Xishuangbanna Botanical Garden is currently breeding species other than Passiflora, including tropical water lilies, Bauhinias, and Jade-leaved Chrysanthemums. They have also achieved some interim results and obtained a variety rights certificate issued by the State Forestry and Grassland Administration. They will continue to innovate in the collection of tropical plant resources and the breeding of varieties.

Planning and production

Produced by Science Popularization China

Author: Mo Haibo and Wu Fuchuan, Xishuangbanna Tropical Botanical Garden, Chinese Academy of Sciences

Producer丨China Science Expo

Editors: Lin Lin, Jin Yufen (Intern)