Some research on the genus Camellia l. (Theaceae) with representatives in Vietnam

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Introduction. The genus Camellia was first established by Linnaeus (1753) in “Species Plantarum” with the first species, Thea sinensis [26]. This species is widely used in China as a beverage with many health benefits [1]. Subsequently, the Thea sinensis species was renamed to Camellia sinensis. This is considered the foundation for later researches on the classification of the Camellia. Since then, the position of the genus Camellia has undergone many changes in the classification systems. Nowadays, it is widely accepted as a genus of the family Theaceae.

A series of recently published discoveries of the Camellia species [9-13; 25; 28; 34; 36; 37; 39; 40; 42-45] led to the fact that the number of species of this genus has continuously increased up to about 280 species [6; 33; 41]. The variation in the number of species as well as the diversity in the morphological characteristics has challenged the differentiation among species in this genus. Therefore, several studies have attempted to divide this genus into sections and sub-genera. Early studies of the genus Camellia classification based on morphological characteristics were performed and widespread [2; 5; 6; 21; 33; 48], being a common traditional classification method, which cannot be a substitute for the classification today. Due to the development of science and technology, many methods based on the anatomy and molecular biology were designed for studying the classification of this genus [19; 47; 50]. Despite the fact that many studies were conducted to classify the genus Camellia, these studies are not entirely consistent. Therefore, research on some of the taxonomic systems of the genus Camellia will serve as the basis for the classification and arrangement of recently discovered species into a consistent system. To implement this research, monographs and articles on the genus Camellia were collected and analyzed. This research focuses on classification systems based on morphological characteristics as well as several systems based on anatomical features and molecular biology techniques.

Classification studies on the genus Camellia in the world. The first understanding of Camellia was a tea tree. Linnaeus (1753) reported this species in “Species Plantarum” with the name Thea sinensis, then renamed Camellia sinensis [26]. He further documented the Camellia japonica, an ornamental plant grown in Japan. Additionally, the author established two genera Thea and Camellia: Thea sinensis belonged to the genus Thea (Class Polyandria Monogynia) and Camellia japonica belonged to the genus Camellia (Class Monadelphia Polyandria). Seemann (1859) is the last author who remained Thea and Camellia names as two distinguished genera [49]. He based on previous research on both Thea and Camellia to document 40 different names, but from his perspective, he narrowed down this number to 12 species of two genera Thea and Camellia.

After Seemann (1859), the two genera Thea and Camellia were merged into a consistent name, Camellia. The authors have divided the Camellia into smaller groups. The first author categorizing the genus Camellia into sections was Dyer (1874). He divided the genus Camellia into two sections (Thea and Camellia), including 14 species [14]. Pierre (1887) classified 16 species into six sections (Camelliopsis, Camellia, Euthea, Calpandria, Piquetia, and Stereocarpus) [46]. Meanwhile, Cohen-Stuart (1916) erased two sections of Pierre (1887) and added one new section [8]. The system of Cohen-Stuart (1916) consisted of 38 species arranged into five sections (Camelliopsis, Camellia, Calpandria, Eriandria, and Euthea). Another author, Melchior (1925) enumerated 50 species belonging to the genus Camellia and divided them into three sub-genera Piquetia, Stereocarpus, and Camellia, in which the sub-genus Camellia was classified into five sections (Calpandria, Eucamellia, Eriandria, Thea, and Theopsis) [30].

Sealy (1958) classified the genus Camellia based on studies with morphological characteristics of Dyer (1874), Pierre (1887), and Cohen-Stuart (1916) [48]. He reused five sections of Cohen-Stuart (1916) and two sections Stereocarpus and Piquetia of Pierre (1886), which were excluded by Cohen-Stuart (1916). He also established five new sections, including Archecamellia, Heterogenea, Paracamellia, Pseudocamellia, and Corallina. Hence, the system of Sealy (1958) had a total of 82 species divided into 12 sections. Until now, it is still considered as a valuable reference for scientists interested in the genus Camellia all over the world (Table 1).

When revising Sealy’s classification system (1958), Chang (1981) retained the two sections Archecamellia and Stereocarpus [3]. However, he moved four species from the Archecamellia section to the new Chrysantha section. In 1996, he reviewed his classification system, removed the Archecamellia section, and retained the Stereocarpus [4]. However, in 1998, the author used these two sections again as a classification system [5]. Contrary to Sealy (1958), Chang removed two sections Heterogenea, Camelliopsis and added 12 new sections, including Protocamellia, Pleurocarpus, Oleifera, Furfuracea, Tuberculata, Luteoflora, Brachyandra, Longipedicellata, Chrysantha, Longissima, Glaberrima, and Eriandriia [5]. Besides, Chang’s system consisted of four sub-genera (Protocamellia, Camellia, Thea, and Metacamellia) divided into 22 sections [5]. Basically, this system is an extended upgrade from Sealy’s system (1958) (Table 1).

Ming and Bartholomew created a new classification system that was based on previous research by Sealy (1958) and Chang (1981, 1998) [31-33]. Compared to previous studies, Ming’s researches was modified a lot. The author divided the genus Camellia into two sub-genera and removed nine sections, including Protocamellia, Pleurocarpus, Oleifera, Furfuracea, Luteoflora, Brachyandra, Chrysantha, Longissima, and Glaberrima. Ming’s systems revived the section Heterogenea from the system of Sealy (1958) [31; 32]. The Heterogenea included the Furfuracea and several species from the Archecamellia and Stereocarpus. The section Archecamellia in his system consisted of the Chrysantha (created by Chang earlier [3]) and the Pleurocarpus. The Stereocarpus was also significantly revised, of which C.dormoyana was retained, the Luteoflora and C.pubipetala (from Chrysantha) were added (Table 1).

Recently, 32 new species were discovered in Vietnam and Southern China. Most of them are in the south of Vietnam. Orel and Curry (2015) based on the system of Sealy (1958), Chang and Bartholomew (1984), Ming and Bartholomew (2007) to arrange these species into a new system [41]. Although the system of Ming and Bartholomew (2007) (the one has significantly reduced the number of sections and the Camellia genus included only two sub-genera) was created after Chang and Bartholomew’s system (1984), Orel and Curry’s system (2015) retained Chang and Bartholomew’s (1984) previous four sub-genera: Protocamellia, Camellia, Thea, and Metacamellia [41]. Compared to Chang and Bartholomew’s system (1984), the sub-genus Protocamellia was removed two sections Protocamellia, Pleurocarpus and added four sections Yersinia, Dalatia, Lecomtia, and Capitatae. Besides, the sub-genus Camellia is preserved, meanwhile, the sub-genus Thea was added to the two sections Lamdongia and Bidoupia, and the sub-genus Metacamellia was added to the section Pierrea. Orel and Curry’s system (2015) was significantly expanded. In this system, the genus Camellia was composed of up to 27 sections in which seven sections were newly created (Table 1).

 

Table 1

The main classification systems of the genus Camellia in the world (underlines are sub-genera, italics are sections)

Sealy (1958)	Chang (1981, 1998), Chang and Bartholomew (1984)	Ming (1999, 2000), Ming and Bartholomew (2007)	Orel and Curry (2015)
Archecamellia Sealy Stereocarpus (Pierre) Sealy Heterogenea Sealy Piquetia (Pierre) Sealy Pseudocamellia Sealy Paracamellia Sealy Camellia (L.) Dyer Corallina Sealy Calpandria (Bl.) Coh. St. Thea (L.) Dyer Theopsis Coh. St. Camelliopsis (Pierre) Sealy	Protocamellia Chang Archecamellia Sealy Stereocarpus (Pierre) Sealy Protocamellia Chang Pleurocarpus Chang Piquetia (Pierre) Sealy Camellia Chang Oleifera Chang Furfuracea Chang Paracamellia Sealy Pseudocamellia Sealy Tuberculata Chang Luteoflora Chang Camellia (L.) Dyer Thea (L.) Chang Corallina Sealy Brachyandra Chang Longipedicellata Chang Chrysantha Chang Calpandria (Bl.) Coh. St. Thea (L.) Dyer Longissima Chang Glaberrima Chang Metacamellia Chang Theopsis Coh. St. Eriandriia Coh. St. Camelliopis (Pierre) Sealy	Thea (L.) Chang Archecamellia Sealy Syn. sect. Chrysantha Chang Thea (L.) Dyer Cylindrica Ming Piquatia (Pierre) Sealy Corallina Sealy Theopsis Coh. St. Eriandriia Coh. St. Longipedicellata Chang Camellia Chang Stereocarpus (Pierre) Sealy Heterogenea Sealy Syn sect. Archecamellia Sealy (sensu H.T. Chang 1981, 1998) Syn. sect Stereocarpus (Pierre) Sealy (sensu H.T. Chang 1981, 1998) Syn. sect. Furfuracea Chang Paracamellia Sealy Tuberculata Chang Camellia (L.) Dyer Calpandria (Bl.) Pierre	Protocamellia Chang Archecamellia Sealy Stereocarpus (Pierre) Sealy Piquetia (Pierre) Sealy Yersinia Orel Dalatia Orel Lecomtia Orel Capitatae Orel Camellia Chang Oleifera Chang Furfuracea Chang Paracamellia Sealy Pseudocamellia Sealy Tuberculata Chang Luteoflora Chang Camellia (L.) Dyer Thea (L.) Chang Corallina Sealy Brachyandra Chang Longipedicellata Chang Chrysantha Chang Calpandria (Bl.) Coh. St. Thea (L.) Dyer Longissima Chang Glaberrima Chang Lamdongia Orel Bidoupia Orel, Curry & Luu Metacamellia Chang Theopsis Coh. St. Eriandriia Coh. St. Pierrea Orel

 

In addition to morphological classification studies, classification methods based on molecular biology techniques, the classification of pollen spores, and the analysis of leaf anatomy have been used. The classification results of Vijayan et al. (2009) published from the nrITS sequence analysis of 112 Camellia species gave both consensus and conflict results compared to previous morphological classification systems [50]. Although the study suggested the polyphyletic nature of the sections Camellia, Paracamellia, Pseudocamellia, and Tuberculata as well as the paraphyletic nature of the section Chrysantha, it did not support the sectional status of three small sections, Archecamellia, Piquetia, and Sterocarpus.

Jiang et al. (2010) conducted a multivariate analysis of leaf shape, anatomy, and Fourier Transform Infrared (FTIR) data of 27 Camellia species with secretory structure (from the sections Archecamellia, Stereocarpus, Furfuracea, and Chrysantha according to Chang’s system (1998)), together with three species from related genera, Gordonia and Tutcheria (Theaceae), to clarify some taxonomic problems [19]. This study indicated that integrated leaf characters based on leaf shape, anatomy, and FTIR data were useful in the taxonomic treatment of Camellia species with secretory structures. The results of this study also tended to support that the Chrysantha species should not be merged into section Archecamellia. Moreover, Jiang et al. (2017) classified Camellia based on the color intensity of red, green, and blue leaves with assistive devices [20]. This study aimed to accurately distinguish 68 species of the Camellia from the five sections Furfuracea, Paracamellia, Tuberculata, Theopsis, and Camellia according to Chang’s classification (1998). As a result, a hierarchical dendrogram and clustering of sections were created.

Lu et al. (2012) used the leaf morphology and venation characters from 93 species of the genus Camellia in five sections, including Furfuracea, Paracamellia, Tuberculata, Camellia, and Theopsis [27]. This study resulted in a clustering dendrogram of sections similar to the previous study. Thus, the analysis of leaf structure data is useful for identifying Camellia species. Lu et al.’s study (2012) complements the traditional studies that used earlier leaf morphological characteristics [27].

Classification studies on the genus Camellia in Vietnam. The earliest study of the genus Camellia in Vietnam was of the French author Lanessan (1886) with the first two species Thea dormoyana and Thea piquetiana [22]. Later, these two species were grouped into the genus Camellia. During the 20th century, the number of authors published researches about Camellia species in Vietnam increased. Gagnepain (1939) additionally published three species Thea amplexicaulis, Thea tonkinensis, and Thea flava [15]. Meanwhile, Chevalier (1919) published the next two species Thea fleuryi and Thea gilberti found in Vietnam [7]. Especially, these are also the first species of the genus Camellia in the world being described as having yellow flowers. In the monograph of Sealy (1958) documented 27 species of the genus Camellia in Vietnam [48], including C. amplexicaulis, C. pleurocarpa, C. krempfii, C. dormoyana, C. piquetiana, C. oleifera, C. furfuracea, C. gaudichaudii, C. kissi, C. corallina, Thea yersini, Thea nervosa, C. nematodea, C. gilberti, C. flava, C. euphlebia, C. petelotii, C. indochinensis, C. tonkinensis, C. fleuryi, C. pubicosta, C. sinensis, C. gracilipes, C. forrestii, C. tsaii, C. tsingpienensis, and C. caudata.

The latter period marked the presence of Vietnamese authors. The authors with typical research on the genus Camellia can be mentioned: Ho (1991, 1999) with “Flora of Vietnam”, Ninh (2002) with “Diversity of Camellia species in Vietnam”, and most recently Hien (2017) with the study on the Theaceae family in “Flora of Vietnam” [16; 17; 18; 35]. Ho (1991, 1999) classified the Theaceae family into ten genera: Anneslea, Archytea, Pyrenaria, Camellia, Gordonia, Eurya, Temstroemia, Tristylum, Adinandra, and Hartia [17; 18]. Of these, the genus Camellia has a superior ovary, an unbundled pistil, large flowers with many bracteoles like sepals, a capsule, and round wingless seeds. He also divided the Camellia into four sub-genera: Protocamellia (Stereocarpus and Archecamellia), Camellia (Camellia), Thea, and Metacamellia. The study of Ho (1999) has recorded and described 30 Camellia species that existed in the territory of Vietnam [18]. This is also considered the first comprehensive systematic announcement dedicated to Camellia species in Vietnam. However, this system was just an application of Chang and Bartholomew’s system (1984) to the Camellia species in Vietnam. According to Ninh (2002), there are 50 species of Camellia in Vietnam [35]. He divided this genus into four sub-genera Protocamellia (Archecamellia, Stereocarpus, and Piquetia), Camellia (Oleifera, Furfuracea, Paracamellia, and Camellia), Thea (Corallina, Branchyandra, Longipedicellata, Chrysantha, Thea, and Longissima), and Metacamellia (Theopsis and Eriandria) [35]. Nonetheless, Ninh’s research (2002) did not provide criteria for classification, as well as classification keys for taxonomic orders in the genus Camellia, and it is based on the system of Chang and Bartholomew (1984) as well. Although Ninh’s system (2002) also included four genera, he classified and expanded the genus Camellia into more sections than the system of Ho (1999) (Table 2).

 

Table 2

Some taxonomy systems of the genus Camellia with representatives in Vietnam (underlines are sub-genera, italics are sections)

Ho (1999)	Ninh (2002)	Hien (2017)
Camellia Chang Camellia (L.) Dyer Thea (L.) Chang Protocamellia Chang Archecamellia Sealy Stereocarpus (Pierre) Sealy Metacamellia Chang	Camellia Chang Camellia (L.) Dyer Oleifera Chang Furfuracea Chang Paracamellia Sealy Thea (L.) Chang Corallina Sealy Brachyandra Chang Longipedicellata Chang Chrysantha Chang Thea (L.) Dyer Longissima Chang Protocamellia Chang Archecamellia Sealy Stereocarpus (Pierre) Sealy Piquetia (Pierre) Sealy Metacamellia Chang Theopsis Coh. St. Eriandriia Coh. St.	Camellia Chang Camellia (L.) Dyer Heterogenea Sealy Stereocarpus (Pierre) Sealy Paracamellia Sealy Thea (L.) Chang  Piquatia (Pierre) Sealy Archecamellia Sealy Corallina Sealy Cylindrica Ming Thea (L.) Dyer Longipedicellata Chang Theopsis Coh. St. Eriandriia Coh. St.

 

Hien (2017) reported 54 species of Camellia in Vietnam [16]. His research was based on Ming’s classification system (1999, 2000), dividing the genus Camellia in Vietnam into two sub-genera and 12 sections. The sub-genus Thea consisted of species with clear peduncle, bracts attached to the peduncle, as well as not deciduous bracts and sepals. This sub-genus included sections Piquetia, Archecamellia, Corallina, Cylindricea, Thea, Longipedicellata, Theopsis, and Eriandria. The sub-genus Camellia was composed of species with almost sessile flowers, sepals closely attached bracts, as well as deciduous bracts and sepals. To divide it into sections, the author based on characteristics such as whether stigmas stick together or separate, the size of the leaf blade is large, medium, or small, and the bracts will soon fall or not. The number of bracts was also used to divide into sections Heterogenea, Stereocarpus, Camellia, and Paracamellia (Table 2).

There are also some other studies on the Camellia in Vietnam that can be mentioned. Ninh (2003) documented 16 species of the Camellia with yellow flowers mostly distributed in northern Vietnam [38]. However, his research does not represent a large number of Camellia species. Moreover, Ninh’s publication did not accompany any descriptions or classifications according to the system. Le and Dung’s collection (2016) of all yellow Camellia species in Vietnam showed that Vietnam had 34 species of Camellia with yellow flowers [23]. However, except for the Camellia with yellow flowers, their study did not report any other Camellia species, as well as classified them into the classification system. Manh et al. (2019) have reported 52 Camellia species with yellow flowers distributed in South China and Vietnam [29]. This study only documented approximately 40 Camellia species existing in Vietnam without determining the exact number of this species in Vietnam. Most recently, Le et al. (2020) has published a list of species of the Theaceae in Vietnam, including the document of 95 species of the Camellia in Vietnam [24]. The number of the Camellia species is very large, but the authors only based on documents without mentioning the research fieldwork. In other words, the authors did not study in detail the taxonomy of the genus Camellia.

It can be stated that the genus Camellia is the largest genus in the family Theaceae that many scientists have concerned about. Many new species were published, many methods were used, and many classification systems were applied. In particular, the classification with morphological characteristics is still considered as the main method which basically cannot be replaced, especially in Vietnamese conditions. Although there are so many classification systems of the genus Camellia in the world and in Vietnam, the ones of Sealy (1958), Chang (1981, 1998), Chang and Bartholomew (1984), and most recently Orel and Curry (2015) are widely recognized. In Vietnam, there are three main systems including Ho (1999), Ninh (2002) and Hien (2017) (Table 2). In which there are two systems of Ho (1999) and Ninh (2002) based on Chang’s system (1998), which was extended by Orel and Curry (2015). These systems are inherited and widely used to classify the genus Camellia with representatives in Vietnam.

Conclusions. This is the first integrated study of the genus Camellia research with representatives in Vietnam. Many classification systems as well as methods have been applied to the classification of the genus Camellia. The traditional classification method based on morphological characteristics is still widely accepted and cannot be replaced in the classification of the genus Camellia both in the world and in Vietnam. Nonetheless, there were not many studies that specialized in classifying the genus Camellia was conducted by Vietnamese researchers. Thus, this study provided an overview of the studies for the genus Camellia with representatives from Vietnam, setting the stage for selecting a suitable system that will be used for the classification study of the genus Camellia of Vietnam.

About the authors

Q. V. Hoi

School of Natural Sciences, Far Eastern Federal University; Tay Nguyen Institute for Scientific Research, Vietnam Academy of Science and Technology

Author for correspondence.
Email: quachvanhoi@gmail.com
ORCID iD: 0000-0002-3691-941X
Russian Federation, Vladivostok; Dalat, Vietnam

D. B. Thin

Hong Duc University

Email: daubathin@hdu.edu.vn
ORCID iD: 0000-0002-6351-3335

Dr. habil.

Viet Nam, Thanh Hoa

B. B. Thinh

School of Natural Sciences, Far Eastern Federal University

Email: buibaothinh9595@gmail.com
ORCID iD: 0000-0002-3826-1199
Russian Federation, Vladivostok

References

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