A Significant Achievement on Camellia Breeding in China

Fifteen Summer-blooming Hybrids Obtained from Crosses between Camellia azalea and Other Camellias

Liu Xinkai, Huang Wanjian, Zhong Naisheng, Chen Guanghui, Feng Guimei and Gao Jiyin
The Academy of Landscape, The palm Landscape Architecture Co., Ltd., China, 510627

As is well known, except for a few of camellia species, such as C. azalea（Gao. 2001. Gao et al. 2008）, C. amplexicaulis (Gao 2002)and C. chuangtsuoensis (Gao et al. 2010), almost all of camellias are blooming in late-autumn, winter or spring. It is obvious that camellias lack summer-blooming or year-round-blooming cultivars (Savige. 1993).

It is, perhaps, because no camellia flowers can be enjoyed in hot summer that makes the world’s camellia people actively create new cultivars using C. azalea which blooms all year-round (King 2010).

The Palm Landscape Architecture Co., Ltd., China has been devoting time to the studies to change camellia blooming period, since 2006. There have been more than 80 cross-combinations that involved in 20 species and 50 cultivars and over 50,000 flowers were used during inter-species crossing with C. azalea at the company’s nursery. We have obtained more than 1500 F1 hybrid seedlings and the seedlings started to bloom continuously from 2010. It has been confirmed with molecular marker determinations and morphology observations that most of the seedlings are true hybrids of C. azalea (Gao et al. 2011). A part of the blooming genes of C. azalea have been successfully transferred into the hybrids.

Here we select 15 hybrids that involved six cross-combinations. These hybrids have bloomed and their characteristics have been steady. The common characteristics of the hybrids are that flowers are bright, flower forms are various,leaves are dark-green, resistances are higher, plants are vigorous and blooming period is from June to December. They can bloom normally under full sun, in which the environmental temperature usually is over 38℃ (100.4℉) in the summer.

1 Presentations of 15 summer-blooming hybrids

1.1  C. azalea X C. japonica’s cultivar A^※

The breeding objective of this group is to get new ones with multi-petals, large flowers or cold-hardiness, besides summer-blooming.

  1-No. 1: Flower buds long-ball-shaped and sepals light-green. Flowers dense, pink, rose-double to formal double form, medium to large, 9-12 cm in diameter, petals over 38, arrangement in order, slight-involute at the edges. Leaves dark-green, broad-elliptic. Plant compact and branches dense. Blooming from Jun. to Dec.

 1-No. 2: Flower buds long-ball-shaped and sepals yellow-green with white pubescence. Flowers dense, pink with some red petals, some deep-red veins visible on the petals, semi-double to peony form, very large, over 13 cm in diameter, petals 37, outside petals arranged in order, inside petals slightly waved, stamens 196, filaments light-red and slightly fused at the base, stigma 7 splits at the tip. Leaves dark-green, coriaceous and edges shallow serrated. Plant spreading and branches dense. Blooming from Jun. to Dec.

1.2  C. japonica’s cultivar B^※ X C. azalea

The breeding objective of this group is to get new ones with large & dense flowers or multi-petals, multi-color or cold-hardiness, besides summer-blooming.

2-No. 1: Flower buds ball-shaped and sepals light-green and slightly white-pubescent. Flowers dense, light-pink, blotched white in centre, single to semi-double form, medium, 8-9 cm in diameter, petals 18, long-obovate, tips slight-cleft and margins involute, stamens over 100 with some petaloids, anthers yellow, filaments light-pink. Leaves dark-green, long-elliptic, thick coriaceous and surfaces shining. Plant both compact and dwarf and growth vigorous. Blooming from Jun. to Dec.

 2-No. 2: Flower buds ball-shaped and sepals yellow-green. Flowers dense, light-red, occasionally some white stripes on petals, anemone form, large, 10-11 cm in diameter, outside large petals 11, long-obovate, inside small petals 114 mixed with a few stamens, filaments milk white. Leaves dark-green, long elliptic. Plant spreading and branches dense. Blooming from Jun. to Dec.

 2-No. 3: Flower buds long-ball-shaped and sepals green with slight white pubescence. Flowers dense, light-red with purple tone, single form, miniature, 5-6 cm in diameter, petals 5-6, broad-obovate, deep-red veins visible on the surfaces, tips slightly curly, stamens many, filaments milk-white. Leaves dark-green, elliptic, coriaceous and surfaces shining. Plant compact and growth vigorous. Blooming from Jun. to Dec.

 2-No. 4: Flower buds ball-shaped and sepals green with a little white pubescence. Flowers dense, light-red, occasionally very narrow white edges on outside petals, anemone form, large, 10-12 cm in diameter, outside large petals 12-13, broad-obovate, inside small petals many, clustered into a ball which is blotched some white and mixed with a few stamens. Leaves dark-green, long-elliptic, Plant spreading and branches dense. Blooming from Jun. to Dec.

 2-No. 5: Flower buds fat-ball-shaped and sepals green with white pubescence. Flowers dense, deep-pink, semi-double to rose-double form, large, 11-12 cm in diameter, petals over 20, ovate, arranged regularly in star-like shape, tips rounded, stamens about 160, filaments pink and slightly fused at the base. Leaves dark-green, elliptic, surfaces shining. Plant compact and growth vigorous. Blooming from Jun. to Dec.

 2-No. 6: Flower buds ball-shaped and sepals light-green. Flowers dense, deep-pink to red, occasionally blotched white, single form, miniature, 5-6 cm in diameter, petals 5-6, broad-obovate with lucency (sheen), tips with tiny splits, stamens about 70-80, filaments white and slightly fused at the base. Leaves dark-green, long-elliptic, surfaces shining, edged with shallow serrations. Plant spreading, branches dense and growth vigorous. Blooming from Jun. to Dec.

 1.3  C. japonica’s cultivar C^※ X C. azalea

The breeding objective of this group is to get new ones with dark-red and dense flowers or cold-hardiness, besides summer-blooming.

3-No. 1 Flower buds longer in shape and sepals 6 and green. Flowers dense, dark-red with hairy texture, single form, medium, 9-10 cm in diameter, petals 7-9, obovate, slightly wrinkled and tips slight-notched, stamens about 90, fused at the base, filaments red and anthers yellow. Leaves dark-green, elliptic and thick-coriaceous. Plant compact and growth vigorous. Blooming from Jun. to Dec. or later.

 1.4  C. azalea X C. japonica’s cultivar D^※

The breeding objective of this group is to get new ones with special color or cold-hardiness, besides summer-blooming.

4-No. 1: Flower buds long-ball shaped, sepals light-green and blooming densely. Flowers claret-red to red, occasionally blotched white, semi-double to rose-double form, medium to large, 8-12 cm in diameter, petals 19, broad obovate, loose-arranged, tips slight-notched, edges involute, stamens 70-100, filaments milk-white and anthers light-yellow. Leaves dark-green, long-elliptic and surfaces shining. Plant upright and growth vigorous. Blooming from Jun. to Dec.

 1.5  C. azalea X C. reticulata’s cultivar E^※

The breeding objective of this group is to get new ones with large & dense flowers, multi-petals or cold-hardiness, besides summer-blooming.

5-No. 1: Flower buds ball-shaped and sepals green. Flowers dense, deep-red, single to semi-double form, medium, 8-9 cm in diameter, petals 17, obovate, tips slightly-notched and surface deep-red veins visible, stamens over 100, occasionally some erect-petaloids occur in the centre and filaments light-pink. Leaves dark-green, long-elliptic, thick-coriaceous surfaces smooth and edges shallow-serrated. Plant compact, branches dense and growth vigorous. Blooming from Jun. to Dec. or late.

 5-No. 2 Flower buds long-spindle-shaped and sepals green. Flowers dense, dark-red, occasionally blotched white, single form, medium, 8-9 cm in diameter, petals 7, broad-obovate, tips slight-notched and surfaces slight-wrinkled, deep-red veins visible on the surface, stamens many and fused into a tube at the base, filaments light-red. Leaves dark-green, shining, edges thinly shallow-serrated. Plant both upright and compact, branches dense and growth vigorous. Blooming from Jun. to Dec.

 5-No. 3 : Flower buds short-ball-shaped and sepals green. Flowers dense, pink with a few white stripes, semi-double to rose-double form, medium, 9-10 cm in diameter, petals 45, outside petals obovate and arrangement regular, central petals slightly wrinkled, stamens clustered, filaments pink. Leaves dark-green, broad-elliptic, shining. Plant compact, branches dense and growth vigorous. Blooming from Jun. to Dec.

 1.6  C. chekiangoleosa X C. azalea

The breeding objective of this group is to get new ones that are very cold-hardy,besides summer-blooming.

6-No. 1: Flower buds long-ball-shaped and sepals green with white pubescence. Flowers separately apical or axillary, light-red, single form, medium, medium, 8.5-9.5 cm in diameter, petals 6-7, obovate, tips deeply notched, stamens 104, filaments pink, fused into a tube at the base. Leaves dark-green, narrow-elliptic, slightly serrated at the edges. Plant spreading, branches soft and growth vigorous. Blooming from Jun. to Dec.

 6-No. 2: Flower buds spindle-shaped and sepals light-green. Flowers pink with many tiny white dots which look like grains of sand, single form, medium, 8-9 cm in diameter, petals 6-7, obovate, slightly wrinkle, tips notched, stamens 180, fused into a tube at the base, filaments light-red. Leaves dark-green, long-elliptic and serrations visible. Plant spread and branches dense. Blooming from Jul. to Dec.

Note: Cultivars A, B, C, D and E with ^※indicate that the cultivars’ names are kept secret temporarily in the paper because of applying patents.

2 Discussions on genetic tendencies of the hybrids

2.1 Genetic tendency on blooming period in the hybrids

  The 15 hybrids contain 50% genes of C. azalea, which can bloom year round, and so the blooming period of the hybrids should be, in a certain degree, changed. Fig.1 shows that the hybrids start to bloom in Jun, in which they are later than C. azalea by 4-5 months and earlier than ordinary camellia cultivars by 3-4 months. From the highest point to the lowest point of blooming, we can see that the hybrids are nearly as same as C. azalea, but different from ordinary cultivars. This tell us that the hybrids only got a part of the genes that control blooming season from C. azalea. Therefore, it is necessary for the hybrids to be back-crossed with C. azalea further.

Fig. 1. Comparisons on blooming period among hybrids, C. azalea and ordinary camellia cultivars

2.2 Genetic tendency on flower characteristics in the hybrids

  The results of the comparisons on color, form and size of flowers in hybrids and their parents are listed in Table 1.

Table 1. Comparisons on flower characteristics in hybrids and their parents

 From Table 1, we can get the following preliminary conclusions on hybrids’ genetic tendencies:

a) Flower color of the hybrids tends towards the parent that has the deeper colored flowers, whether C. azalea is the female or male parent. White colored flowers are recessive to red flowers, so the hybrids do not have any white ones, even though a white parent was used, such as 4-No.1; however, if the flowers of another parent in a cross-combination are white blotched or striped, its hybrid will occasionally be blotched white or striped. If the flowers of the double parents in a cross-combination all are red, their hybrids will be red or pink, such as 5-No.3, 6-No.2 etc.

  b) Flower forms in the hybrids tend towards their father or mother. C. azalea is single. If another parent in a cross-combination is semi-double, anemone or peony, the hybrid will be single (which is like C. azalea’s), semi-double, rose-semi-double, peony or formal double, such as 1-No.1 to 1-No.2, 2-No.1 to 2-No.6, 4-No.1 and so on. If the other parent is single, the hybrid must be single, such as 6-No.1 and 6-No.2.

c) Flower sizes in the hybrids are very complex. Usually, parents with large flowers can produce large flowers’ hybrids, however, a few of hybrids with small or miniature flowers also can occurred, such as 2-No.3 and 2-No.6.

2.3 Genetic tendency on characteristics of leaves and plants in the hybrids

  According to our measurements, the leaves of the hybrids all are dark-green and long-elliptic shaped which is slightly similar to C. azalea. Most of the hybrids plants are compact in habit, dense in branches and vigorous in growth, which are also very similar to C. azalea. It should be pointed that in the cross-combination, C. chekiangoleosa X C. azalea, the hybrids mostly tend to C. chekiangoleosa both in leaves and plants.

From the above, we can see that C. azalea is not only a high-heterozygote, but also a high-breeding-potential species. Our research is only just starting to use it in hybridization. We are sure that with the increasing quantity of C. azalea’s hybrids being produced, the arrival of camellias that bloom all year round will be coming to us in near future soon.

References:

Gao Jiyin. 2001. C. azalea promises new horizons for camellia culture, American Camellia Yearbook, 8-9.
Gao Jiyin, Huang Wanjian, Liu Xinkai. 2008. Camellia azalea, the ever-blooming camellia. International Camellia Journal, 40: 89-96.
Gao Jiyin. 2002, Talking about C. amplexicaulis, American Camellia Yearbook, 22-25.
Gao Jiyin, Xinkai Liu, Wanjian Huang, Yulin Liu, Guanghui Chen. 2010, Camellia chuangtsoensis, another re-blooming species discovered after Camellia azalea in China, International Camellia Journal, 84-89.
Thomas J. Savige. 1993. The international camellia register, Volume one, The International Camellia Society,
Bradford King. 2010, An empirical study of camellia azalea and camellia amplexicaulis germination, American Camellia Yearbook, 22-26.
Gao Jiyin, Liu Xinkai, Huang Wanjian, Cheng Guanghui, Zhao Qiangmin, 2011. Researches on Inter-species-cross of camellia azalea and its 5 summer-bloomed hybrids, , the First International Symposium on Historic Camellias and Conservation in Japan.