Studies on the Origin of Camellia x wabisuke

 Takayuki Tanaka
School of Agriculture, Tokai University, Minami-aso-mura, Aso-gun, Kumamoto 869-1404, Japan

Introduction

Wabisuke camellia have been very popular in Japan for a long time because of the Japanese preference for its tiny single flower rather than gorgeous double flowers, especially at the Japanese tea ceremony, where they prefer to decorate the room with the flower of Wabisuke camellia.  More than twenty cultivars of Wabisuke camellia were found in Japan.

Typical cultivars of Wabisuke camellia show small cupular lavender-pink single flowers, with pubescent ovaries. Oblanceolate-elliptic or broad elliptic leathery leaves with the teeth prominently and regularly serrulate to almost serrate,.  These characteristics are not found in the normal C. japonica.  While Wabisuke camellia has some anomalous characteristics such as much reduced or abortive androecium and the imperfect ovules which are sometimes observed in the interspecific hybrids.  Therefore, Wabisuke camellia has been considered as being of hybrid origin from the early times despite the fact that their parentages were not clarified.

At first, Wabisuke camellia was scientifically described as a variety of Camellia reticulata, Thea reticulata var. Wabiske by Makino (1910).  Nakai (1950) reclassified Wabisuke camellia to C. cuspidata for 'KochÔ-wabisuke' and 'Sukiya', C. rosaeflora for 'TarÔkaja' ( = 'Momoiro-wabisuke' ) or hybrid origin.

Then Kitamura (1961 and 1965) thought it was a hybrid between C. sinensis and C. japonica with a note that the leaf of 'Uraku' was similar to that of C. pitardii.  Kondo (1976) considered it as an intraspecific variation of C. japonica because Wabisuke camellia showed the morphological traits similar to C. japonica.

While the author could not imagine the possibility of C. pitardii as one of the parents of the Wabisuke camellia, because C. pitardii var. pitardii introduced from Australia had small compact leaves.  It was now considered as C. saluenensis.  In 1980 when the real C. pitardii ( C. pitardii var. pitardii ) was introduced from China, Kirino, Hakoda and the author hit upon the idea that C. pitardii is one of the parents of Wabisuke camellia.  The image of the characteristics of the F₁ hybrid between C. pitardii and C. japonica is that of 'TarÔkaja' for us.  Tanaka (2001) also pays attention to the small brown spots ( tanniferous cork warts ) on the undersurface ( abaxial surface ) of the leaf which was observed only on the leaf of C. japonica in the genus Camellia.  All of the cultivars of Wabisuke camellia have them.  In our former paper (Tanaka 2001), the authors wrote a paper on the origin of Camellia wabiske in 2001 that 'TarÔkaja' is a primary hybrid between C. pitardii and C. japonica and other cultivars of Wabisuke camellia are the backcross generation with C. japonica from the morphological and historical consideration.  Then Wabisuke camellia were renamed as Camellia x wabiske ( Kitam. ) T. Tanaka from Camellia wabiske Kitamura.  ‘x’ is a denotation to indicate that the species is of  hybrid origin.

After then Tanikawa et al. (2010) make clear, by the ctDNA analysis, the maternal parentage of the Wabisuke camellia On the other hand, the study of chromosome numbers was a pre-requisite for the breeding project of the plants and also for the study to make clear the origin of putative hybrid species.  The cytological studies on the genus Camellia was carried out by Fukushima, Kondo, Tanaka and others.  Here, the author adds the data on the chromosome numbers and karyotypes of Wabisuke camellia.

Materials and Methods

 The oldest records of each of eighteen cultivars of Wabisuke camellia were surveyed in the old books and catalogues published in Japan.  Then the place and their girth size of oldest trees discovered in Japan and their flowering seasons were studied.  Morphological characteristics of Wabisuke camellia and species of the section Camellia were surveyed either on the young cuttings or the adult trees. 

Thirteen cultivars of Wabisuke camellia were studied cytologically.  Root tips were taken from three year old cuttings.  They were pretreated in 0.002 mol 8-hydroxyquinoline for five hours, hydrolyzed immediately ( without storage ) in 1N HCl for 15 minutes and stained in basic Fukushin.  Slides made by squash method were frozen and then the cover slips were removed.  Finally, the preparations were restained with Giemsa's solution.  Karyotype analyses were carried out under microscopes.

Results and Discussion

Morphological characteristics of nineteen cultivars of Wabisuke camellia and seven species of the section Camellia are shown in Table 1 and 2, respectively.  In the present study, we focused on the typical Camellia x wabiske that had certain characteristics that differed from C. japonica.  While there are so-called Wabisuke camellias, some are not really C. x wabiske:- 1) 'Yae-wabisuke' is a cultivar of C. x vernalis ; 2) 'Aka-wabisuke', 'Kuro-wabisuke' and 'Kon-wabisuke' are cultivars of C. japonica which have small bell type single flowers similar to the Wabisuke camellia and 3) 'Ichiko-wabisuke' and 'Sado-wabisuke' are bud-mutated cultivars of C. japonica which have the aborted androecium. 

Table 1.  Morphological characteristics of the cultivars of Camellia wabiske

 Leaves of typical Wabisuke camellia were oblong-elliptic or oblanceolate-elliptic or broad elliptic, abruptly acuminate to caudate, base cuneate.  The edge of the leaves were prominently and regularly serrulate to almost serrate, the teeth 1 - 2 mm apart, and other characteristics of the leaves were thinly leathery, glabrous, dark green above, blight green below and nervation visible on both surfaces.  Small brown spots ( cork warts ) existed on the leaf abaxial surface of all of the cultivars of Wabisuke camellia.  The small brown spots were observed only on the leaves of C. japonica, but not on those of C. pitardii and other species ofthe genus Camellia.

Table 2.  Morphological characteristics of the species in section Camellia

 Most of cultivars of Wabisuke camellia used in the present study had terminal and/or axillary, solitary or geminate, small, cupular and purplish rose-pink flowers consisting of 5 or 6 petals.  The androecia were adnate to the abortive or reduced except 'TarÔkaja', 'SeiÔbo', 'MishÔ' and 'Miyo-no-sakae'.  The ovules were atrophied and seed fertilities were very low except 'TarÔkaja', ' SeiobÔ', 'MishÔ' and ‘Kaga-wabisuke’, indicating that they are hybrid origin.  The ovaries were tomentose or pubescent like C. pitardii except 'Sukiya', 'Owari-wabisuke', 'Mikawa-sukiya' and 'EishÔji-wabisuke'.  Most of these cultivars grow compact except 'TarÔkaja', 'SeiÔbo', and 'Miyo-no-sakae'.

By these characteristics, Wabisuke camellia could be easily distinguished from C. japonica, and showed greater similarity to both C. pitardii and C. japonica than any other Camellia species. 'TarÔkaja' especially was very similar to C. pitardii, as was suggested by Kitamura (1965).  However, small brown spots on the abaxial surface of the leaves which existed frequently only in C. japonica were observed as well as in other cultivars of Wabisuke camellia studied.

The year of issues of the books or catalogues, the sources and the girth sizes of the old trees of twenty cultivars of Wabisuke camellia are shown in Table 3 mainly from the survey by Kirino (1971, 1982 and 1986).  The first record of C. x wabiske was 'KochÔ-wabisuke' ( 'Wabisuke' ) in the Japanese book ' Kadan-Chikinsho' published in 1695.  Then 'TarÔkaja' appeared in 1739 in the book 'Honzo-Hanamakie'.  However, 'TarÔkaja' must be the oldest cultivar of C. x wabiske from the estimated age( ca. 300 - 400 years old ) of the tree discovered recently in Momigio village, Miyazaki Prefecture, Kyushu Island, Japan. It is 243 cm in girth. Seven other old trees (> 130 cm) were found in Miyazaki Pref. and also in Honshu Island, Japan, where many old trees found, 185 cm tree in Tottori Pref., 165 cm tree in Nara Pref., 110 cm tree in Kyoto City and others ( Shizuoka Pref., Mie Pref. and Tokyo ).  Though Nara and Kyoto were the old capitals in Japan before Tokyo, Momigio is located in a very remote, mountainous small village. 

In Edo period, Japan was politically isolated from other countries except Port Dejima, Nagasaki Pref. which traded with the Netherlands and China and illegal foreign trade through Satsuma ( old name of Kagoshima Pref.) via Ryukyu ( Okinawa Pref.) both in Kyushu Island.  Horticulture was so popular then that they might import exotic plants from there.  The imported plants might not survive the long journey to Edo ( old name of Tokyo ) or Kyoto, indicating that they might be planted somewhere else in Kyushu Island temporarily.  In fact, sweet potato is called 'Satsuma'-imo in Japanese which is considered to be named after the imported place, Satsuma.  In addition, the name of the cultivar of the oldest Camellia reticulata tree ( ca. 200 - 300 years old ) planted at Kitadani , Dazaifu, Fukuoka Pref., Kyushu Island was 'Satsuma-kurenai' ( synonym of the ‘Captain Rawes’ ) from China.  Thus, Satsuma ( Kagoshima ) had an important role in introducing foreign plants and Miyazaki is the neighboring prefecture of Kagoshima. 

Therefore, the authors considered the three steps in the distribution of Wabisuke camellia:- the first place where C. pitardii was introduced was Satsuma, then ‘TarÔkaja’ was established and planted in Miyazaki prefecture, and finally it spread to other places of Japan.  Now we can understand the reason why the oldest tree of Wabisuke camellia was planted not in the old, big and developed city, Tokyo or Kyoto but in one of the most rural places in Japan.  Furthermore, ‘TarÔkaja’ could be looked back to before 1549 if ‘Usuiro-tsubaki’ was the synonym of ‘TarÔkaja’ from the record of the Japanese tea ceremony by Kirino (1996).

Species of the genus Camellia have strong self-incompatibility (Tanaka, 1986) and Camellia pitardii planted alone might not set any fruit if it had not been pollinated by the pollen of the allied species, C. japonica which grew wild abundantly there.  Therefore, when seeds were obtained, the probability of the seedling being their F₁ hybrid is reasonably high. 

After the above two cultivars, 'Hatsukari' ( 1739 ), 'Shibenashi-wabisuke' ( 1789 ), 'Shiro-wabisuke' ( 1844 ), 'Sukiya' ( 1879 ), 'Beni-wabisuke' ( 1879 ), 'SeiÔbo' ( 1947 ) , 'Hina-wabisuke' ( 1960 ), 'Kanzaki-aka-wabisuke' ( 1960 ), 'Fukurin-wabisuke' ( 1960 ), 'MishÔ' ( 1969 ), 'Owari-wabisuke' ( 1970 ), 'Mikawa-sukiya' ( 1973 ), 'Hime-wabisuke' ( 1974 ), 'Sagami-wabisuke' ( 1974 ), 'Miyo-no-sakae' ( 1975 ), 'Kaga-wabisuke' ( 1975 ) and 'EishÔji-wabisuke' ( 1976 ) were released to the public and relatively old trees of them were discovered in Japan ( Table 3 ).

Table 3.  Published year of the oldest literature and the place ( girth in cm ) of the old trees of the cultivars
of  C. wabiske

 In the previous paper, all of the cultivars of C. x wabiske, 'Kotyo-shiro-wabisuke' and 'Usu-wabisuke' ( 2n = 2X = 30 ) reported by Kato and Shimura ( 1971 ), 'Usu-wabisuke' and 'Sukiya' ( n = X = 15 ) reported by Kato and Shimura ( 1970 ) and  'Sukiya' by Kondo ( 1975, 1976, 1981 ) 'SeiÔbo' by Fukushima et al. (1966 ) were diploid ( 2n = 2X = 30 ).

In the present study, ‘TarÔkaja’, 'KochÔ-wabisuke', 'Beni-wabisuke', 'Shiro-wabisuke',  'Fukurin-wabisuke', 'Hina-wabisuke', 'Kanzaki-aka-wabisuke', 'Sayo-wabisuke', , 'Shibenashi-wabisuke', and 'Showa-wabisuke' were also found diploid, suggesting that the parents of these cultivars were diploid.  From the chromosome number of the C. x wabiske, one of the parents is considered to be C. pitardii ( = C. pitardii var. pitardii ) but not C. pitardii var. yunnanica ( = C. reticulata ).

Only 'Miyo-no-sakae' was triploid cultivar ( 2n = 3X = 45 ).  In the genus Camellia, most of the wild species are diploid or hexaploid except tetraploid species, C. granthamiana and some triploid individuals occasionally found both under cultivated and natural conditions.  From the morphological point of view, 'Miyo-no-sakae' was a cultivar of C. x wabiske.  Generally, the appearance of triploid individuals is very low when the parents are diploid.  In the F₂ progeny between the two diploid species in the same section, however, unexpected triploids occurred at a rate of more than 10 % between Lactuca sativa and L. saligna.  As C. pitardii and C. japonica belong to the same section and we considered that the most cultivars of C. x wabiske were BC₁ between them, it was reasonable enough to appear the triploid.

Karyotypes of 13 cultivars of C. x wabiske and two cultivars of Wabisuke-like camellia are shown in  Table 4.  Two Wabisuke-like camellia, 'Kuro-wabisuke', 'Kon-wabisuke', were also diploid ( 2n = 30 ) as well as C. japonica though they do not have any characters of C. pitardii. All of the karyotypes of C. x wabiske studied were not identical.  'Shibenashi-wabisuke' had three satellite chromosomes, and 'Sayo-wabisuke', and 'Miyo-no-sakae had four satellite chromosomes.

Table 4.  Karyotypes of C. x wabisuke and  C. japonica confused with C. x wabisuke

Fukushima et al.(1966) reported that the karyotype of C. japonica was 2n = 16V + 8J + 2J^t + 4v, and then Kondo (1975) reported a big intraspecific diversity in the karyotypes that 21 accessions of C. japonica had different karyotypes from each other.  Thus, from the karyotype analysis, we could not estimate the parents of C. x wabiske.

In the book of Sealy (1958), typical C. reticulata in the narrow sense was a species known as a group of gorgeous double flower cultivars but not found in wild and C. pitardii was divided into two varieties, C. pitardii var. pitardii and C. pitardii var. yunnanica.  The two varieties are exclusively distributed in China and have different chromosome number, 2n = 30 and 2n = 90, respectively.  The single flower type of C. reticulata introduced to Japan from China in 1980 was considered to be C. pitardii var. yunnanica.  Then C. pitardii var. yunnanica is reclassified as a wild form of the C. reticulata.  Among the big intraspecific variation of the C. pitardii discovered in China, white flower to deep purple flower, the C. pitardii introduced to Japan in 1980 gave us the idea that C. pitardii is one of the parents of Wabisuke camellia.  In fact, the chromosome numbers of Wabisuke camellia were diploid 2n = 2X = 30 except triploid 'Miyo-no-sakae', indicating the possibility of the parent of Wabisuke camellia is C. pitardii introduced to Japan in about 400 years ago, but not hexaploid C. reticulata (= C. pitardii var. yunnanica).

While the 'TarÔkaja' sets capsules ( fruits ) occasionally and the open-pollinated seedlings were more or less similar to the 'KochÔ' type cultivars of Wabisuke camellia ( Kitamura, 1970; Kirino 1971, 1982, 1986 ), indicating that they are offspring of ‘TarÔkaja'.  Some of them have reduced or abortive androecium and compact ( weak ) growth which characteristics are observed in the back cross generation.  As the species of the genus Camellia has strong self-incompatibility ( Tanaka, 1986 ), most of the seedlings from the ‘TarÔkaja' might be reasonably hybrid ( BC₁ generation ) with the abundant C. japonica.  BC₁ is a segregating generation and the odd combination of the alien genes causes both the deficiency and vigorousness of the progeny. 

The rest of cultivars of Wabisuke camellia other than 'TarÔkaja' are classified into two groups ; 1) Cultivars of Wabisuke camellia in the narrow sense and 2) ‘SeiÔbo’ type.  ‘KochÔ-wabisuke’ is a typical cultivar of the former group which has small sized flowers with atrophied androecium and some of the cultivars are intermediate type.  In Japan, Wabisuke camellia is exclusively defined as cultivars related to ‘TarÔkaja’ in origin with the abortive androecium.  At this point, ‘SeiÔbo’ is not counted as a Wabisuke cultivar because of its normal androecium in the medium sized flower though it obviously has characters which originated from ‘TarÔkaja’ or ‘Kaga-wabisuke’.  Cultivars of Wabisuke camellia in the narrow sense do not set any seeds because of the abortive androecium and ovary.  Therefore, from not only these historical records and the oldness of the trees but also their morphological characteristics, the authors (2001) advocated defining Camellia x wabiske ( Kitam. ) T. Tanaka et al. as cultivars of Wabisuke camellia in the broad sense which include F₁ hybrid ( 'TarÔkaja') and/or back cross generation ( mostly BC₁ ) between C. pitardii and recurrent parent, C. japonica. 

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