Copyright 1998-2004 by Yoshiaki Yoneda
Complete identification of gene linkage groups
What problems are left or could be pursued in the future of the morning glory that have been useful as study materials in genetics since the beginning of the 20th century? First, one big problem left unfinished from the classic genetics period is the creation of a gene linkage map. In classical genetic studies, 10 linkage groups were recognized in the morning glory, Ipomoea nil. So, identification of the remaining 5 linkage groups would complete the gene linkage map for the morning glory. Dr. Eiji Nitasaka of Kyushu University is solving this problem currently by using new techniques in molecular genetics.
Flower color and floral design
Recently, the mechanisms of some kinds of flower color patterns that appeared in the Edo era by deassociation of transposons from color synthetic genes have been demonstrated by Prof. Shigeru Iida et al. of the National Institute for Basic Biology. This work may be developed to elucidate some mutable morphological characters in relation to transposons in the future. Because the Japanese morning glory is a treasurefull of many gene mutants affecting the flower, leaf and stem, the work of Prof. Iida's team will be very useful to our understanding of the organization of higher plants.
Breeding of a yellow flower
To breed a yellow flower is a for many cultivators of the Japanese morning glory. Here is a figure of an intense yellow flower in a morning glory gardening book from the Edo era. However, in pigments of the petal of Japanese morning glory, there are flavonoids such as blue, purple and red anthocyans and light yellow chalcones or aurons, but not the carotenoid pigments expressing intense yellow color. Because a light yellow flower of the large-flowered Japanese morning glory is already cultivated, one direction of breeding is toward intensifying this light yellow pigment. The wrier tried to increase the yellow color by crossing gene i (intense) to intensify the flower color to the light yellow flower strain "Ukon" and then selecting yellow flowers through several generations. However, although he managed to produce intense yellow buds, only light yellow flowers opened. There are intensely yellow-flowered species of Tutanohahirugao (Merremia hederacea), Budouhirugao (Merremia vitifolia) and Wood Rose (Merremia tuberose). However, they are distantly related to the Japanese morning glory. Though it is impossible to cross them to the Japanese morning glory by conventional methods, a new breeding technique of gene introduction may be applied in the future.
Morning glories Ipomoea nil (=Pharbitis nil)|
The flower was obtained by crossing a strain having gene i (intense, color-intensifying gene) with Ukon (light-yellow flower strain), then by selecting the descendants repeatedly. The yellow color of the flower didn't become intense.
Morning glories Ipomoea nil (=Pharbitis nil)|
This flower was obtained by the same selection. It has a considerably intense yellow in a bud or a flower of incompletely opened flowers.
Do we have any methods to improve flower durability? In the varied morning glory, Kikyou (star) strains have a highly durable flower called the two-day flower because the flower preserves its shape till the day after flower-opening. Its color changes, however. The Kikyou strains have thick, stiff-feeling leaves. However, these strains seem to be worthless for improving the flower durability of the large-flowered strain, because they have small flower diameters. As Yojiro (Ray white) morning glory, with the genes of Ipomoea purpurea, has many strains with excellent flower durability, it might improve the durability of large-flowered strains to some extent. Because Yojiro (Ray white) large flowers are cultivated now, would they not be useful as crossing materials for ordinary large-flowered strains?
The withering of a flower is demonstrated to be caused by the outbreak of ethylene. Therefore, inhibiting the enzymes concerned will reduce the withering. One method to preserve the flower is to spray on it, or have the plant absorb, a substance that inhibits withering. As for other methods, there is a method to obstruct the action of this enzyme by gene introduction. The latter method has already been successful with the breeding in durable tomatoes. The gene introduction in Ipomoea nil could be realized by using the individual regeneration techinique from an adventive embryo as the starting material, which the author developed.
Breeding by interspecific crossing
In the interspecific hybrid bred by Y. Yoneda, the Youjiro (Ray white) morning glory, which was raised from the hybrid of the morning glory, Ipomoea nil, and the common morning glory, Ipomoea purpurea, has excellent flower durability, multifloral character and resistance to cold. All of these features are derived probably from the latter species. The Ray white is now popular as a flower giving clear color impression to the Japanese morning glory. More interesting flowers may be created if we could magnify their characteristics.
In addition, the author is very much interested in using perennial Noasagao (Ipomoea indica) in morning glory (Ipomoea nil) breeding, though it is impossible to cross the two species to produce their hybrid. When pollens of Ipomoea indica were applied to an Ivyleaf morning glory (Ipomoea hederacea), the immature embryos developed at an extremely early stage after fertilization, then their breakdown occurred. Thus, in the future we might get a hybrid individual if we could rescue the immature embryo at this stage by in vitro culture. The author considers this a possible interbridge for morning glory (Ipomoea nil) breeding.
As explained in the item on "tissue culture", if we could produce an entire plant from a piece of tissue or a cell, we could bring up a new plant by introducing a gene from another plant. From this point of view, the regeneration system of the immature embryos of Ipomoea nil will be useful for a gene introduction system. A gene introcduction experiment with Ipomoea nil is currently under way. This method may be effective for breeding a yellow flower, for improving flower durability, and so on.
The author has observed the morning glory (Ipomoea nil) as a single organism in the history of the earth and various aspects, mainly from a biological point of view. Homo sapiens has also had a long history as another creature of the earth, though human beings have also achieved an existence through culture. The maximum point of contact between we Japanese and the morning glory (Ipomoea nil) is Asagao, the morning glory of the Edo era, as a horticultural flower. This flower is the current successor morning glory. The author thinks it would be splendid to have cultural interchange between Japan and many parts of the world through the traditional flower of the morning glory. We are able to do this in the age of the Internet. This technology is very useful for the promotion of mutual understanding between different cultures. The author expects that this morning glories image database, with the cooperation of other researchers, will develop into a large network encompassing all items of culture.
- Araki, T., Hirano, H., Naito, S. and Komeda, Y. (1989) Intoroduction of foreign genes into Pharbitis nil calli using a vector derived from Agrobacterium pTi. Plant Cell Reports 8: 259-262.
- Otani, M. and Shimada, T. (1998) Embryogenic callus formation from immature embryo of Japanese morning glory(Pharbitis nil Choisy) Plant Biotechnology15: 127-129.
- Ono, M., Sage-Ono, K., Kawakami, M., Hasebe, M., Ueda, K., Masuda, K., Inoue, M. and Kamada, H. (2000) Agrobacterium-mediated transformation and regeneration of Pharbitis nil. Plant Biotechnology 17: 211-216.
- Yoneda, Yoshiaki (2006) Edo Gardening Morning Glories. Gakken (in Japanese)
- Yoneda, Yoshiaki (2011) On the Form and Beauty - Brief History of Enjoying the Japanese Morning Glory - Biostory vol.16:38-45 The Society of Biosophia Studies (in Japanese)
- Yoneda, Yoshiaki (2012) Mainly on the Horticultural History of the Japanese Morning Glory: In Morning Glories p.12-24. Seibundo-Shinkosha Publishing Co. (in Japanese)
Edited by Yuuji Tsukii (Lab. Biology, Science Research Center, Hosei University)