Yellow flowered hybrids produced from cross-combination with non-yellow Camellia Species

Liu Xin-Kai  Zhong Nai-Sheng  Feng Gui-Mei  Yan Dan-Feng  Gao Ji-Yin*
The Academy of Landscape, Palm Landscape Architecture Co. Ltd., China 510627

Background

A dream to obtain yellow flowered camellia cultivars has been started since yellow camellia species, especially C.nitidissima, were discovered. Although the road to develop yellow camellia cultivars was long and hard^[1], some light-yellow flowered cultivars have been created with different breeding avenues^[2]. It was the yellow flowers of yellow camellia species that made camellia people firstly thought to move the yellow genes into their expectant hybrids, and so a lot of hybridizations had been done using C. nitidissima which the flower color is the most yellow as a cross-parent, by camellia breeders around the world^[3]. It is roughly checked out that Mr. Kazuo Yoshikawa and Mr. Tadao Yamaguchi who were as the representatives of yellow flowered camellia breeding enthusiasts in Japan got about 20 hybrids which their flowers were yellow or yellow tone. Of the hybrids, ‘Shoko’, ‘Kicho’, ‘Ki-no-moto 95’and ‘Kagirohi’ were famous in the Camellia World because of their yellow flowers, multi-petals and high ornamental value^[4]. In the United States，Nuccio’s Nurseries Inc., a very famous on camellias, had made many crosses between C. nitidissima and other camellia cultivars and had obtained 4 first generations hybrids which of them, the most outstanding hybrids were ‘Golden Glow’ with light-yellow and semi-double and ‘Honeymoon’ with cream yellow^[5]. Dr. Gene Phillips who lived in Georgia, also got a hybrid named ‘Alice B. du Pont’ bred from a cultivar of C. japonica crossed with C. nitidissima. Professor Clifford Parks, the most famous yellow camellia hybridizer got a yellow tone hybrid named ‘Solstice’ bred from C. flava crossed with a cultivar of C. japonica. Mr. Huang Liandong in Nanning Yellow Camellia Garden of Guangxi China has been doing crosses of yellow camellia species recent years and has raised many hybrid seedlings. He published two new variety named as ‘Jinbei Danxin’ with light red but yellow color on back surfaces of its petals^[6] and ‘Dongyue’ with yellow color respectively^[7].

Does yellow camellia species have to be used as cross-parents for getting yellow flowered Hybrids? The answer is negative. The chance C.japonica seedlings or hybrids whose parents show no hint of yellow in their petals, in fact, also can produce yellow flowered or yellow-tone flowered cultivars. Mr. W.F. Homeyer Jr., U.S.A. For examples, selected a yellowish cultivar named ‘Witman Yellow’ which is the first yellow cultivar in the world, fromC.japonica seedlings in 1963^[8]. The second yellow camellia cultivar named ‘Gwenneth Morey’ with cream-yellow and anemone form was selected from ‘Edith Linton’, a C.japonica cultivar, by Dr B.R. Morey, Australia in 1965^[9]. The third yellow camellia cultivar named ‘Brushfield’s Yellow’ with light-yellow color and anemone form was selected from C.japonica seedlings by Mr. Keith Brushfield, Australia in 1970^[10]. The fourth yellow one named ‘Dahlonega’ with Canary yellow and formal double was obtained from aC.japonica cross-combination, ‘Witman Yellow’ X [seedling x (‘Elizabeth Boardman’ x ‘Colonial Dame’)], by W.F. Homeyer Jr., U.S.A^[11].

From above, we must think highly of using non-yellow Camellia species as cross-parents，while using yellow Camellia species as cross-parents when crossing, in order to get yellow camellia cultivars. We found an example that can get yellow hybrids in a cross-combination without any yellow camellia species during our camellia breeding work. We report it as below now:

1 Materials and methods

Cross-combination:

‘Tama Beauty’（A cultivar of C. japonica）x C. amplexicaulis

Cross method:

It was done in the spring, 2006. Ten flower buds which just will open were selected on a plant of ‘Tama Beauty’, took off all of the stamens from the buds, put fresh pollens of C. amplexicaulis on the stigmas, covered a paper bag on each of the buds and labeled them. Two pollinated flowers were only fruited in the 10 pollinated flowers. The hybrid capsules were took off after maturing in September of 2006, 11 seeds were gotten from the 2 capsules and then sown them into a suitable medium immediately. Seven seeds were germinated and when the seedlings grew up to over 20 cm high, they were moved into a plant bed which has fertile soil. There were 2 of the 7 hybrid seedlings bloomed firstly in the spring of 2010 and labeled as H-No.1 and H-No.2 respectively. The characteristics of their flowers, plants and growth were measured in detail. Also, the hybrid plants were cultivated in eastern China for measuring their cold hardness in winter.

2 Results

Both H-No.1and H-No.2 all are pale-yellow in flower color, but the former is soft in branches and spread in growing and the latter is pale-yellow with some light-pink in flower color and upright in its growing.

2.1 Flower characteristics

H-No.1: Flower buds dense, ball-like, sepals 10, yellow-green, back-surface white-pubescent. Flowers pale-yellow, semi-double, petals 32, arranged in order, elliptic, round and slightly outward-inclined at the tip, medium in size 8.5-10.5 cm in diameter, stamens about 150,1.9-2.1 cm long, densely arranged, united at the base, filaments light-yellow, anthers yellow, pistil 1 cm long, 7-9 splits at the tip. Blooming period of them is from winter to next spring. The flowers of H-No.2 is nearly a same as H-No.1, but the flower buds are light-pink during extension phase and petals are very light-pink at the edges when flowers fully open.

It would be pointed that the two hybrids are different from their cross-parents on flower color and shape. See table 1.

Table 1. Comparisons of flower characteristics in hybrids and their cross-parents

Hybrids and their cross-parents	Flower photo	Flower color	Flower form	Flower size	Blooming period
H-No.1		Pale-yellow	Semi-double	Medium	Winter to next spring
H-No.2		Pale-yellow with light-pink tone	Semi-double	Medium to large	Winter to next spring
Female parent (Tama Beauty)		Red with white edges	Semi-double	Medium to large	Winter to next spring
Male parent (C. amplexicaulis)		Light-red to red	Single	Small to medium	Autumn to next summer

2.2 Leaf characteristics

The leaves of the two hybrids all tend to their male parent on leaf size, but the leaves are much thicker than the female parent and much thinner than the male parent. Please see table 2.

Table 2. Comparisons of leaf characteristics in hybrids and their cross-parents

Hybrids and their cross-parents	Leaf photo	Leaf length (cm)	Leaf width (cm)	Thickness(mm)
H-No.1		12.0 ± 0.9	5.1 ± 0.1	0.88 ± 0.05
H-No.2		11.6 ± 1.3	4.8 ± 0.4	0.93 ± 0.08
Female parent (Tama Beauty)		6.4 ± 0.3	3.4 ± 0.3	0.75 ± 0.05
Male parent (C. amplexicaulis)		23.8 ± 1.5	8.6 ± 0.9	1.90 ± 0.10

2.3 Growth vigor

The hybrids have obviously growth vigor comparing with their cross-parents on average annual growth. Based on the determinations, the numbers of the annual growing of the hybrids were3-4 times and the total annual growth was about 80 cm in length, which the hybrids are 5 times of the female parent, ‘Tama Beauty’ and 2 times of male parent, C. amplexicaulis (See Fig.1). This growth habit of the hybrids provided a possibility that they could be used for gardening.  

Fig. 1 Comparison among the hybrids and their cross-parents on average annual growth

2.4 Resistances

It has been shown that the female parent, ‘Tama Beauty’, of the hybrids belongs to C. japonica and has a strong cold-hardy, therefore it can safely grow in winter in eastern China. Meanwhile, the male parent, C. amplexicaulis, is no cold-hardy and cannot resist to the cold weather in area of eastern China ^[12]. With cultivation experiments in different area, the hybrids show high summer heat resistance and strong winter cold hardness. They can normally grow well under temperature 40℃ in summer and temperature -5℃ in winter (table 3.).

Table 3. Comparisons of the leaf resistances of the hybrids and their parents under extreme temperatures

3 Discussions

Some very famous pale-yellow camellia cultivars which are not any blood relationship of yellow camellia species were obtained in the United States and Australia early or late, during the selecting chance seedlings from C. japonica cultivars in early period. These show that yellow camellias breeding is not the one way that yellow camellia species must be used as cross-parents to arrive the yellow goal. The two hybrids we got are the ones with non-yellow camellia species and they all are not any relationship to yellow camellia species, but can open pale-yellow flowers. It has been shown again that yellow camellias can be gotten from the hybridizations which are done with other camellias out of yellow camellia species. Our hybrids are another true example that yellow flowered hybrids produced from cross-combination without any yellow camellia species.

The cross-parents do not open yellow flowers but their hybrids can open yellow flowers, why?

With the cross-combination we did, we inference that the possible reasons of yellow color appearing in the F₁ are that: a) both female, ‘Tama Beauty’ and male, C. amplexicaulis, all contain yellow genes which they have not yet expressed out, b) only one of the cross-parents contains yellow genes which they have not yet expressed out and c) both of the two cross-parents all do not contain any yellow genes, but their gene re-combinations specially changed during the process of crossing between them, which conduced to the yellow color expressions in the F₁ hybrids. Of course, these inferences would be researched further in the future.  

According to the successful results obtained from the crosses among yellow camellia cultivars which they are non-yellow camellia species, the two hybrids we got also can be used for crossing with other yellow camellias. It can be expected that the hybrids as cross-parents will be, in some degree, potential, to create new yellow camellia hybrids.

Also，the two hybrids grow very strongly, have high resistances and can be cultivated in the areas of southern China and eastern China. Therefore, they are good camellia hybrids for gardening.

Literature cited

[1] Chen Junyu. 1987. Forty Years for Breeding New Yellow Camellia Varieties. Journal of Beijing Forestry University, 9(5):315-319
[2] Wu Hormish. Yang Jiangfan. Zhan Zijin. 2004. Advance of Yellow Camellias on Cultivation and Breeding. Jour of Fujian Forestry Sci and Tech, 31 (3):147-150
[3] Clifford R. Parks. 2000. Breeding Progress with Yellow Camellias. American Camellia Yearbook, 9-10
[4] Saburo Yokoyama, Kirino Shuho. Camellias of Japan. Tankosha Publishing Co., Ltd. 2005
[5] Bradford King. 2011. The Wonderful Hybrid Camellias. American Camellia Yearbook, 76-87
[6] Huang Liandong. Jiang Changjie. Li Zhihui. 2011. AnInter-species Hybrid bred with C. nitidissima as Cross-parent, proceedings of the ^stWenzhou Cross-Strait Symposium on Conservation and Exploitation of Camellias Annual Chinese Camellia Breeding Meeting, 125-127
[7] Huang Liandong. Li Zhihui. 2012. An excellent cultivar derived from F₂ hybrid of Camellia nitidissima.2012 Proceedings of The International Camellia Congress, 169-171
[8] Southern California Camellia Society. 1999. Camellia Nomenclature, edited by Arthur A. Gonos, 122, 164-165
[9] Tom Durrant. 1982. The Camellia Story, Heinemann Publishers, 121-122
[10] Don Ellison. 1997. Camellias, A Photo Dictionary. Flora Publications International Pty, Ltd. 26
[11] Gao Jiyin. Su Yuhua. Hu Xiancong. 2007. The Identification and Appreciation of The World’s Outstanding Camellias, Zhejiang Science & Technology Publishing House, 69
[12] Gao Jiyin. 2002. Talking about Camellia amplexicaulis. American Camellia Yearbook, 22-24

 *Author for correspondence: Gao Ji-Yin, Professor, y25006@163.com