TheTeaPlantsBotanicalaspects - Rodrigo Gonzalez (4)

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CHAPTER 1
The Tea Plants: Botanical
Aspects
F.N. Wachira1,3, S. Kamunya1, S. Karori2, R. Chalo1, T. Maritim1
1Tea Research Foundation of Kenya, Kericho, Kenya
2Department of Biochemistry, Egerton University, Egerton, Kenya
3ASARECA, P.O. Box 765, Entebbe, Uganda
3
Abbreviations
AFLP amplified fragment length polymophism
EC (�)-epicatechin
ECG (�)-epicatechin gallate
EGC (�)-epigallocatechin
EGCG (�)-epigallocatechin gallate
EST expressed sequence tag
F1 first filial generation
GA gallic acid
GABA gamma aminobutyric acid
GC (�)-gallocatechins
GCG (�)-gallocatechin gallate
IPGRI International Plant Genetic Resources Institute
LSI late acting prezygotic gametophytic self incompatibility
PPO polyphenol oxidase
RAPD random amplified polymorphic DNA
RFLP restriction fragment length polymorphism
SSR simple sequence repeat
STS sequence tag site
TF theaflavins
TI Terpene Index
TR thearubigins
INTRODUCTION
The cultivated plant species Camellia sinensis ((L.) O. Kuntze) is the source of the raw material
from which the popular tea beverage is processed. The species is now cultivated commercially
in Asia, Africa and South America. Major producers of the crop include China, India, Kenya,
Sri Lanka and Indonesia (Table 1.1). Kenya is currently the largest single exporter of tea (Table
1.2). Although the crop is cultivated in many countries, there are several different types of tea
plant, each with its own identifiable character and potential for unique cup quality. Because of
this diversity, it is important that the different types of tea plant can be told apart and be
classified. Classification, in the biological sense, is the ordering of plants into a hierarchy of
classes. The product is an arrangement or system of classification designed to express
Tea in Health and Disease Prevention. DOI: 10.1016/B978-0-12-384937-3.00001-X
Copyright � 2013 Elsevier Inc. All rights reserved.
http://dx.doi.org/http://dx.doi.org/10.1016/B978-0-12-384937-3.00001-X
TABLE 1.1 World Production of Tea (Metric Tons) and Percent Share
Country
Year
2006 2007 2008 2009
Prod. % Vol. Prod. % Vol. Prod. % Vol. % Vol.
China 1,028,064 28.7 1,140,000 30.0 1,200,000 32.5 1,358,642 34.5
India 981,805 27.4 944,678 25.9 980,818 25.4 978,999 24.9
Kenya 310,578 8.7 369,606 9.7 345,817 8.9 314,198 8.0
Sri Lanka 310,822 8.7 304,613 8.0 318,697 8.2 289,774 7.4
Indonesia 146,847 4.1 137,248 3.6 137,499 3.6 136,481 3.5
Others e Africa 172,052 4.8 189,845 5.1 172,022 4.5 201,767 5.1
Others 629,481 17.6 664,904 17.7 649,337 16.9 656,235 16.6
World Totals 3,579,649 100.0 3,750,894 100.0 3,804,190 100.0 3,936,096 100.0
TABLE 1.2 World Exports of Tea (Metric Tons) and Percent Share
Country
Year
2006 2007 2008 2009
Amount % Vol. Amount % Vol. Amount % Vol. % Vol.
China 286,594 18.2 289,431 18.4 296,935 18.1 302,949 19.2
India 215,672 13.7 175,841 11.2 193,000 11.8 193,000 12.2
Kenya 312,156 19.8 343,703 21.8 383,444 23.4 342,482 21.7
Sri Lanka 314,915 19.9 294,254 18.7 297,469 18.2 279,839 17.7
Indonesia 95,339 6.0 83,659 5.3 96,210 5.9 92,304 5.9
Others e Africa 139,575 8.8 156,558 10.0 144,317 8.8 162,886 10.3
Others 214,317 13.6 229,279 14.6 226,560 13.8 204,583 13.0
World Totals 1,578,568 100.0 1,572,725 100.0 1,637,935 100.0 1,574,428 100.0
4
SECTION 1
Tea, Tea Drinking and Varieties
inter-relationships and to serve as a filing system. The term ‘classification’, however, is often
used for both the process of classifying and for the system which it produces.
CLASSIFICATION IN CAMELLIA
The tea plant (Camellia sinensis) from which the beverage tea is processed, is placed in the
genus Camellia. The genus has over 200 species and is largely indigenous to the highlands of
Tibet, north eastern India and southern China (Sealy, 1958). Sealy (1958) classified the genus
into 12 subgeneric sections, one of which (Thea) contains species of cultivated tea. However, in
his monograph Sealy recognized a group of 24 inadequately known species which he called
‘Dubiae’ (Dubious). In their work, Chang and Bartholomew (1984) not only translated the
1981 monograph of the genus Camellia by H.T. Chang but also included publication of new
taxa andmovedmany species treated by Sealy to different sections. They divided the genus into
four subgenera (sub groups), i.e. Protocamellia, Camellia, Thea and Metacamellia, and twenty
sections (Figure 1.1).
Taxonomy of the genus Camellia has been complicated by the free hybridization between
species, which has led to the formation of many species hybrids (Chuangxing, 1988). Simi-
larly, most species are unavailable to scientists for study. Genetic relationships and taxonomy
has therefore remained controversial and recent interest has seen the discovery of many new
species and a revision of taxonomic relationships (Chuangxing, 1988; Lu and Yang, 1987;
Tien-Lu, 1992). Tea is, however, the most important of all Camellia spp. both commercially
and taxonomically. Though the other non-tea Camellia’s are not widely used to produce the
Genus Camellia
C. granthamiana
+ 2 other species
5 species
Protocamellia
Sect. Piquetia
Sect. Stereocarpus
Sect. Archaecamellia
C. sasanqua
C. oleifera
+ 2 other species
C. furfuracea
+ 7 other species
Camellia
Sect. Paracamellia
Sect. Furfuracea
Sect. Oleifera
12 species
2 species
Sect. Carollina
Sect. Longipedicallata
Sect. Calpedicellata
Sect. Brachyandra
C. kwangsiensis
C. quinquelocularis
C. tachangensis
C. crassicsolumna
C. pentastyla
C. taliensis
C. irrawadiensis
C. crispula
C. gymogyna
C. costata
C. yunkiangensis
C. leptophyla
C. pubicosta
C. angustifolia
C. sinensisvar. sinensis
var. assamica
var. waldenae
var. publilimba
C. fangchensis
C. ptilophyla
C. parvisepale
Sect Thea
Sect. Glaberrima
Sect. Longissima
C. pitardii
C. saluensis
C. japonica
+ 13 other species
6 species
Sect. Pseudocamellia
Sect. Camellia
Sect. Luteoflora
Sect. Tuberculata
C. kissi
C. brevistyla
C. miyagii, + 13 other species
5 species
1 species
11 species
4 species
Sect. Chrysantha
10 species
2 species
C. tsaii
C. lutchuensis
C. fraterna
C. rosaeflora
C. nokoensis
+ 37 other species
Metacamellia
Sect. 
Camelliopsis
Sect. Theopsis
C.assimilis
C.salicifolia
+ 12 other species
TheaSubgenera
FIGURE 1.1
Summarized Schematic Diagram Showing Species Relationships within Genus Camellia.
CHAPTER 1
The Tea Plants: Botanical Aspects
5
brew that goes into the cup that cheers, several species, e.g. C. taliensis, C. grandibractiata,
C. kwangsiensis, C. gymnogyna, C. crassicolumna, C. tachangensis, C. ptilophylia, are used as
sources of tea-like beverages in parts of China, which indicates that the economic potential for
beverage production from additional underutilized species is very great (Tien-Lu 1992; Chang
and Bartholomew, 1984). Seed oil from several species including C. fraterna, C. japonica and
even C. sinensis are important sources of cooking oil in China. In addition, many Camellia
species are of great ornamental value.
At the species level, tea taxonomy failed to attract much attention and interest once the species
of economic importance were identified. It continues to be a low-priority area in most tea
research programs. The array of hybrids available which might suggest unrestricted intro-
gression of many species of Camellia and tea compound the taxonomic jigsaw. Several minor
taxa have been treated as conspecific with major taxa, although more recently accumulated
evidence has shown that these minor taxa have no natural distribution and are derived from
hybridization events involving different species (Parks et al., 1967; Uemoto et al., 1980). The
taxonomic affinities of most interspecific and intraspecific hybrids are unknown, but could
provide clues to the evolutionary organization of the tea gene pool. Information on taxonomic
characteristics, genetic diversity and biogeography of Camellia in living collections are scantily
documented, though vital in identifying sources of desirable genes (Banerjee,1992).
Tea was initially classified as Thea sinensis by Linnaeus (Linnaeus, 1753). Following the
discovery of its economic importance, and the subsequent extensive collection of indigenous
tony
Highlight
TABLE 1.3 Criteria U
Variety S
China
Camellia sinensis
var. sinensis (L.)
C
s
p
S
C
s
m
S
Assam
Camellia sinensis
var. assamica
(Masters) Kitamura
SECTION 1
Tea, Tea Drinking and Varieties
6
teas from the forests contiguous to the upper AssameBurmaeTibet borders, two distinct taxa
were identified and classified byMasters (1844) as Thea sinensis, (the small-leaved China plant)
and Thea assamica (the large-leaved Assam plant). For a long time, Thea and Camellia were
considered as separate genera (Fujita et al., 1973) and some authors even considered Camellia
to be a ‘section’ under the genus Thea (Roberts et al., 1958; Barua and Wight, 1958).
Another group of authors (Sealy, 1958; Barua, 1965) considered that CameIlia and Thea were
so much alike in morphological, anatomical and biochemical features that the classification
schemes proposed above were unrealistic. According to them, the apparent difference in leaf
pose, patina and pigmentation was a part of the total variation in leaf features. Wight (1962)
considered Thea to be synonymous with Camellia and the name Camellia prevailed. Thus,
today tea is botanically referred to as Camellia sinensis (L.) O. Kuntze, irrespective of species-
specific differences.Camellia sinensis is classified under section Thea along with 18 other species
(Figure 1.1).
At the species level, several intergrades resulting from unrestricted intercrossing between
disparate parents have been documented, but have not been assigned the status of separate
species (Sealy, 1958). However, three distinct tea varieties have been identified on the basis of
leaf features like size, pose and growth habit. These are the China variety, Camellia sinensis, var.
sinensis (L.); the Assam variety, Camellia sinensis var. assamica (Masters) Kitamura; and the
southern form also known as the Cambod race, C. assamica ssp. Lasiocalyx (Panchon ex Watt).
The three main taxa can be differentiaed by foliar, floral and growth features (Tables 1.3 and
1.4) and by biochemical affinities (Sanderson, 1964; Robert et al., 1958; Hazarika and
Mahanta, 1984; Ozawa et al., 1969; Fujita; et al., 1973; Owuor et al., 1987). It is common to
find the three different varieties (China, Assam and Cambod) referred to as separate species,
namely, Camellia sinensis, C. assamica and C. assamica ssp. Lasiocalyx, respectively (Bezbaruah,
1976). Research has shown that cultivated tea is an out-crosser with an active late-acting pre-
zygotic gametophytic self incompatibility (LSI) system (Wachira and Kamunya, 2005a; Muoki
et al., 2007). Because of its out-breeding nature and, therefore, high heterogeneity, most
cultivated teas exhibit a cline extending from extreme China-like plants to those of Assam
origin. Intergrades and putative hybrids between C. assamica and C. sinensis can themselves be
arranged in a cline of specificity (Wight, 1962). Indeed because of the extreme hybridizations
between the three tea taxa, it is debatable whether archetype (original) C. sinensis, C. assamica
or C. assamica ssp. lasiocalyx still exist (Visser, 1969). However, the numerous tea hybrids
currently available are still referred to as Assam, Cambod or China depending on their
morphological proximity to the main taxa (Banerjee, 1992).
sed for Differentiating Two Major Tea Varieties and Sub-Varieties of Camellia sinensis
ub-Varieties Growth Habit Leaf Characteristics Leaf Pose
Leaf
Angle
. sinensis var.
inensis f.
arviflora (Miq)
ealy
. sinensis var.
inensis f.
acrophylla
ieb (Kitamura)
Dwarf, shrub-like,
slow growing
Small, erect, narrow,
serrate, dark green in
colour
Erectophile
(directed
upwards)
<50�
Tall, tree stature,
quick growing
Large, horizontal pose,
broad, mostly non-serrated,
light green in colour
Planophile
(horizontal)
<70�
TABLE 1.4 Types of Tea Differentiated on the Basis of Foliar Characteristics
Morphological Characteristics Leaf Type
1 2 3 4 5
Mean area of an individual leaf (cm2) 11.8 37.2 65.0 152.4 46.0
Length/breadth ratio 2.5 2.3 2.0 2.4 2.8
Mean internode length below plucking
surface (cm)
1.7 3.4 5.0 6.6 3.0
Mean leaf angle from vertical (degrees) 26 29 87 99 28
Angle formed by halves of lamina (degrees) 105 120 162 189 161
Patina Matt Matt Glossy Highly
glossy
Glossy
Leaf area index of mature bush 8.55 5.34 4.22 3.64 4.38
1 ¼ Extreme China
2 ¼ Typical between Assam and China
3 ¼ Typical between Assam and China
4 ¼ Extreme Assam
5 ¼ Close to 2
(Scheme as used by Hadfield (1974))
CHAPTER 1
The Tea Plants: Botanical Aspects
7
Recent revisions of taxonomy within section Thea have led to identification and description of
additional varieties of C. sinensis, namely var. waldenae (Hu) (Chang and Bartholomew 1984),
var. dehungensis (Chuangxing, 1988) Ming, and var. publimba (Chang) (Tien-Lu, 1992). In
Taiwan, a new subspecies of wild tea C. sinensis ssp. buisanensis (Sasaki) Lu and Yang, has been
described (Lu and Yang, 1987).
Wood and Barua (1958) and Cannell et al. (1977) have raised doubts regarding whether or not
the existing tea populations have resulted from natural hybridizations between the three main
taxa only, or have also involved other Camellia species. Ackerman (1973) described inter-
specific crosses between tea Camellias and C. kissi and C. sasanqua. The presence of some tea
clones with brick red or purple pigmented leaves may be an indication of possible species
hybridization (personal observation; Kerio et al., 2012). According toWight and Barua (1957),
the presence of punctate leaf forms in some tea hybrids provides further evidence of the natural
hybridization of both C. sinensis and C. assamica with C. irrawadiensis (a non-tea Camellia)
which has similar punctations. The hybrids described, however, produce commercially low-
quality tea. Based on this experience, introgression from wild species into the gene pool of tea
may not always be beneficial, as this could adversely affect quality attributes (Banerjee, 1992).
Indeed, thoughmost non-tea Camellias, e.g. C. irrawadiensis, C. taliensis, C. reticulata, C. pitardii,
C. saluensis, C. sasanqua, C. japonica, C. lutescens, C. kissi, C. caudata, C. rosaeflora, C.
hongkongensis, C. cuspidata, superficially resemble tea, they either lack caffeine or produce weak
infusions which may not pass as quality tea. Directed species hybridization may, however,
break this rule with the development of high-quality interspecific hybrids. Indeed presently,
many interspecific hybrids of tea and other Camellia species have been developed, for example
with C. japonica (Bezbaruah and Gogoi, 1972; Takeda et al., 1987). C. taliensis (Fuchinoe,
1975), C. irrawadiensis (Bezbaruah, 1975), C. sasanqua (Fuchinoe, 1975), C. kissi (Bezbaruah
and Saikai, 1977) and C. caudata (Bezbaruah and Saikai, 1977). Special focus has, however,
been made on two taxa, C. irrawadiensis and C. taliensis. These two taxa closely resemble C.
sinensis variety assamica in leaf and growth characteristics but lack caffeine, with C. irrawadiensis
containing an analog of caffeine, theobromine. Because of the aforementioned, the liquors of
C. irrawadiensis and C. taliensis lack the quality of tea. All F1 interspecific hybrids created
between these two species and C. sinensis have also failed to produce a tea of commercially
acceptable quality. Most of these have very low caffeine levels though when one of the C.
sinensis X C. irrawadiensis, hybrids was back-crossed to C. sinensis, it gave high-quality, high-
yielding progeny (Bezbaruah, 1987). The prospect of using interspecific hybrids for improving
stress tolerance traits, e.g. cold hardiness, drought resistance, disease and pest resistance, and
SECTION 1
Tea, Tea Drinking and Varieties
8
specific characters in biochemical components, without necessarily impairing quality, there-fore exist and need to be exploited further. Nevertheless, it is generally accepted that only three
taxa, C. assaica, C. sinensis, C. assamica ssp. lasiocalyx, have contributed to the gene pool of
cultivated tea. Thus, the term ‘tea’ is often used to include the above taxa and their hybrids. The
contribution of the recently described varieties, waldenae, dehungensis, publimba and subspecies
buisanensis, to cultivated tea is as yet unknown.
METHODS OF DISTINGUISHING TYPES OF TEA
One of the key elements in classification is description. Description is the orderly technical
recording of characteristics of a group, particularly the morphological ones. A diagnosis is
a short comparative description, stating only those characters which differentiate the taxon
from its closest allies in the same rank. Characterization calls for development of suitable
descriptors for elucidating differences between tea plants. Ideally such descriptors should not
be affected by plant development and growth environment.
MORPHOLOGICAL TRAITS
Though the tea plant can grow to become an under tree or even a tree, cultivated plants are
maintained as a low bush in a continuous vegetative phase of growth by cyclic pruning every
three to five years to form a plucking table. Because of this cultural practice, it has become
essential that vegetative characteristics be used to describe and differentiate tea taxa. However,
because of its outbreeding nature and high heterogeneity, most of its vegetative, biochemical
and physiological characteristics show continuous variation and high phenotypic plasticity
(Purseglove, 1968; Wickremasinghe, 1979; Wickremaratne, 1981; Banerjee, 1988; Magoma
et al., 2000; 2003). Despite this, leaf macromorphological features, e.g. leaf color, size and
pose; leaf angle and leaf area index; have been widely used as descriptors in tea taxonomy,
although chemotaxonomy (Takeo, 1983; Owuor et al., 1987; Magoma et al., 2000; Kerio et al.,
2012) and molecular (DNA) taxonomy (Matsumoto et al., 1994; Wachira et al., 1995, 1997,
1999; Paul et al., 1997; Kaundun and Matsumoto, 2002), have also been applied.
The International Plant Genetic Resources Institute (IPGRI) has published a standardized
descriptor list for tea (IPGRI, 1997). This list provides an international format for character-
ization in a universally understandable ‘language’ for tea genetic resources data. Traditionally,
leaf and floral morphology, and growth habit have been the more important criteria for
assigning taxonomic categories within Camellia. The standardized descriptor list of the IPGRI
also includes such novel methods as chemical profiling, e.g. for catechin content and Terpene
Index; biochemical markers, e.g. isoenzymes; cytological markers, e.g. chromosome number,
meiosis chromosome associations, identified and sequenced genes, etc.; and the more esoteric
molecular marker fingerprint profiles, e.g. restriction fragment length polymorphisms (RFLP),
random amplified polymorphic DNA (RAPD), amplified fragment length polymorphism
(AFLP), simple sequence repeats (SSRs), sequence tag sites (STS), and expressed sequence tags
(EST), etc.
The vegetative characteristics generally used in assigning taxonomic categories in tea include:
leaf size (leaf length, leaf breadth), ratio of leaf length to breadth, internode length, length and
girth of bud, petiole length, ratio of apical length, angle between leaf tip and axis, leaf margin,
shoot density, etc. Although these related characteristics may overlap and show continuous
variation, restricting their usefulness in characterization somewhat, they continue to be widely
used by tea growers and scientists the world over. Based on growth habit and leaf features, the
major varieties of tea have been distinguished as the China and Assam varieties, as shown in
Table 1.3. This classification scheme identifies two separate sub-varieties of the China variety:
f. parviflora and f. macrophylla. It is difficult to distinguish between f. parviflora and f. macro-
phylla, except that the former possesses extremely small (1.5e6.0 cm long; 1.2e2.0 cm wide)
CHAPTER 1
The Tea Plants: Botanical Aspects
9
and the latter relatively large (4.0e14.0 cm long; 2.0e2.5 cm wide) leaves (Bezbaruah, 1976).
It is doubtful if these two taxa still exist in existing commercial tea populations, and whether or
not they can be set apart from C. sinensis var. sinensis. They possibly represent a part of the total
variation in leaf features in the chinary type of tea (Bezbaruah, 1976). Purseglove (1968)
mentions a third variety, C. sinensis var. macrophylla Makino from Japan. It is a large-leaved
triploid (2x ¼ 3n ¼ 45), and gives a bitter decoction.
Based on foliar characteristics, Hadfield (1974) recognizes five types of tea, each with distinct
and quantifiable foliar characteristics. Though these types are not separate taxa, the variations
in their foliar attributes can be related to either extreme China or extreme Assam plants (Table
1.4). Hadfield (1974), quoting Purseglove (1968), did not consider the involvement of any
variety other than Assam and China in accounting for the variation in leaf characteristics in the
five types of tea.
The grouping of tea into the erect, small-leaved China variety and the horizontal, broad-leaved
Assam variety was rather subjective because plants with intermediate leaf characteristics could
not always be assigned to either of these two varieties. Only on the basis of leaf angle, for
example, can tea be classed as erectophile (leaf angle <50�, planophile (leaf angle >70�, or
oligophile (leaf angle 50e70�). While China and Assam types generally cover the erectophile
and planophile plants respectively, the oligophiles are far too distinct to come under any of the
two main varieties. Despite this limitation, leaf features continue to be widely used to classify
tea and to study the extent of variation between cultivated taxa.
An example is presented in which some vegetative traits are evaluated in a collection of Kenyan
tea clones (Table 1.5). In the example, the Assam and Cambod varieties had larger leaves and
leaf pose angle than the China variety. The tetraploid clones in particular had very large leaves.
The non tea Camellias, i.e. C. irrawadiensis and C. japonica, had leaves of similar dimensions to
those of the Assam variety. Using hierarchical cluster analysis and the leaf size traits (length
and breadth) of the first four leaves (Nos. 1e4), it was possible to distinguish the China variety
clones from the rest (Table 1.6). The TRFK clone Dwarf, which has extreme China character-
istics, clustered alone. In this assay, the C. irrawadiensis and C. japonica clustered with the Assam
varieties. A similar analysis using the leaf pose angles and leaf internodes gave different clusters
with the former, distinguishing the Cambod clone TRFK 301/3 and the latter again distin-
guishing the TRFK clone Dwarf. A combination of all the traits did not improve the resolution
of clustering; this meant that leaf size alone was fairly useful in discriminating varieties of
Kenyan tea. This has also been confirmed by the use of other statistical analysis methods, such
as principal component analysis (Wachira, unpublished). This further demonstrates the power
of leaf traits in differentiating tea taxa.
Leaf anatomical differences and particularly the variation in distribution and morphology of
sclereids in leaf lamina have also been useful for differentiating tea varieties. Cambod clones
have numerous sclereids compared to Assam and China clones. Similarly, sclereids in Cambod
tea have wider lumen when compared to those of the other varieties (Barua and Wight, 1958).
Leaf trichome hairs have also been used to identify some tea taxa (Amma, 1986). Stomata, leaf
anatomical features and stomatal conductance have also been used to characterize tea clones
(Ng’etich and Wachira, 2003).
Unlike foliar features, floral morphology can also provide reliable diagnostic criteriafor
differentiating various tea taxa and classifying them into discrete groups. However, because tea
in production is maintained at a vegetative phase of growth by cyclic pruning, these features
are not widely used and are not considered in this article.
CYTOLOGICAL MARKERS
The main varieties of tea are diploids (2n ¼ 30), and their chromosome structures are also
comparable; even C. irrawadiensis conforms to 2n ¼ 30. The chromosome number of several
TABLE 1.5 Vegetative Traits in Some Kenyan Tea Clones
Clone
Leaf 1 Leaf 2 Leaf 3 Leaf 4 Internodes
Variety/Type PloidyD Length Breadth Length Breadth Length Breadth Length Breadth Leaf 1e2 Leaf 2e3 Leaf 3e4
AHP S15/10 Assam Diploid 6.325
�
2.3 9.535
�
3.9 10.740
�
4.4 9.435
�
4.8 2.5 4.8 5.7
BBK 35 ” ” 6.840
�
2.2 9.840
�
3.5 9.840
�
3.5 13.440
�
5.2 2.6 4.5 4.3
TRFK 31/8 ” ” 6.215
�
1.9 9.140
�
2.9 11.845
�
4.2 13.145
�
5.0 1.1 2.7 4.0
AHP 31/37 ” ” 8.035
�
2.6 11.745
�
4.1 14.650
�
5.4 15.450
�
5.6 2.3 4.8 4.7
TRFK 382/1 Assam Triploid 7.040
�
2.5 12.245
�
4.6 12.570
�
5.4 13.650
�
6.0 1.4 2.2 2.2
TRFK 386/2 ” ” 6.630
�
2.5 13.650
�
5.7 13.960
�
6.2 15.060
�
7.1 1.8 3.2 3.6
TRFK 311/287 ” Tetraploid 9.045
�
3.3 12.255
�
5.0 12.750
�
5.0 10.660
�
4.7 2.2 2.5 2.6
TRFK 31/30 ” ” 9.845
�
3.7 12.455
�
5.9 13.945
�
5.2 12.660
�
5.7 3.1 4.0 4.7
TRFK 301/1 Cambod Diploid 6.245
�
2.1 8.440
�
3.4 11.845
�
4.9 11.645
�
5.1 1.9 3.5 3.5
TRFK 301/3 ” ,, 7.025
�
2.3 11.270
�
3.8 14.035
�
4.7 14.580
�
5.0 2.2 4.7 4.5
TRFK 301/4 ” ,, 8.145
�
2.1 13.050
�
3.5 15.535
�
4.2 14.340
�
4.5 1.9 2.7 3.7
TRFK 301/5 ” ,, 7.440
�
2.3 10.645
�
3.4 16.345
�
5.4 16.960
�
5.6 2.1 4.0 6.6
TRFK 56/89 China Diploid 5.030
�
1.4 7.245
�
2.1 9.140
�
2.6 7.945
�
2.7 2.2 4.2 4.0
TRFK China 1 ” ,, 4.530
�
1.0 7.140
�
1.7 9.340
�
2.3 9.335
�
2.7 0.8 1.5 2.1
TRFK China 2 ” ,, 3.125
�
1.1 5.130
�
1.7 7.045
�
2.6 8.035
�
3.1 1.3 3.0 3.5
TRFK Dwarf ” ,, 2.015
�
0.5 3.030
�
0.9 3.545
�
1.1 3.645
�
1.1 0.5 0.6 0.8
K/purple ” ,, 3.315
�
1.2 5.635
�
2.0 7.040
�
2.6 5.950
�
2.4 1.2 2.7 2.7
*C. irrawad. Non tea ,, 6.330
�
1.9 10.735
�
3.1 13.035
�
4.2 13.640
�
4.5 1.6 3.5 2.7
**C. japonica Non tea ,, 6.540
�
3.2 10.745
�
4.1 11.450
�
4.7 12.050
�
5.0 0.7 3.0 3.0
Superscript, leaf base angle.
þploidy, no of chromosomes, i.e. diploid ¼ 2x ¼ 2n ¼ 30, triploid ¼ 45, tetraploid ¼ 60
*Camellia irrawadiensis
**Camellia japonica
S
E
C
T
IO
N
1
T
e
a
,
T
e
a
D
rin
k
in
g
a
n
d
V
a
rie
tie
s
1
0
TABLE 1.6 Cluster Membership of Tea Clones Using Average Linkage (Between
Groups) Analysis
Clone
Cluster Number (Group)
Leaf Sizes
(1e4)
Leaf Pose
Angles (1e4)
Leaf Internode Lengths
(1e2, 2e3, 3e4)
DCombined
Traits
AHP S15/10 1 1 1 1
BBK 35 1 1 1 1
TRFK 31/8 1 1 2 1
TRFK 31/37 1 2 1 2
TRFK 382/1 1 2 2 2
TRFK 386/2 1 2 2 2
TRFK 311/
287
1 2 2 2
TRFK 31/30 1 2 1 2
TRFK 301/1 1 1 2 1
TRFK 301/3 1 3 1 3
TRFK 301/4 1 2 2 2
TRFK 301/5 1 2 1 2
TRFK 56/89 2 1 1 1
TRFK China 1 2 1 2 1
TRFK China 2 2 2 2 1
TRFK Dwarf 3 1 3 1
TRFK K/
purple
2 1 2 1
*C. irrawad. 1 1 2 1
**C. japonica 1 2 2 2
þAll the combined traits
*C. irrawadiensis
**C. japonica
CHAPTER 1
The Tea Plants: Botanical Aspects
11
‘wild’ tea (e.g. C. caudata and C. kissi), is also of 2n ¼ 30 as in cultivated tea. This constancy in
diploid chromosome number might suggest a monophyletic origin of all tea species, including
perhaps C. irrawadiensis and other Camellia species. Deviations from normal chromosome
number are however more common in Japanese Camellia taxa than in taxa from other areas.
C. sasanqua is a hexaploid or tetraploid (2n ¼ 90 or 2n ¼ 60), C. sinensis var. macrophylla is
a triploid (2n ¼ 45) and C. rosaeflora, a tetraploid with 2n ¼ 60.
Cultivated tea forms a stable polyploidy series. Natural triploids, tetraploids and aneuploids
have been sampled in tea populations in Japan, India and Kenya, but are reportedly present in
very low number (Wachira and Kiplangat, 1991; Wachira, 1994). Generally, rooting ability, leaf
size and dry-weight of polyploids as well as total polyphenol content are higher than those of
diploids (Wachira, 1994: Wachira and Ng’etich, 1999; Magoma et al., 2000). Pollen viability
and fertility of triploids are, however, usually poor; with tetraploids being more fertile than the
triploids, but less than the diploids (Wachira and Kiplangat, 1991). Studies carried out on
different tea cultivars have revealed that chromosome complements of tea comprise of near
metacentric to submetacentric chromosomes (Bezbaruah, 1975; Wachira et al., 1999).
Nucleolar number in tea has been demonstrated to correspond to multiples of the somatic cell
number and is a good marker for ploidy in the species (Wachira and Muoki, 1997). Cyto-
logical investigations in tea have, however, been restricted mostly to determination of chro-
mosome number rather than explaining the cytological basis of species differentiation. For
example, it is not known whether, in view of similarities in chromosome morphology and
identical chromosome numbers, species differentiation in tea started from the same basic
genome, or different species and taxa had diverse origins. Detailed studies on chromosome
morphology in different hybrids might be helpful in elucidating the cytological relationship.
tony
Highlight
tony
Highlight
tony
Highlight
SECTION 1
Tea, Tea Drinking and Varieties
12
CHEMICAL/BIOCHEMICAL TRAITS
Chemical profiling has also been used to characterize species within the genus Camellia
(Nagata, 1986). Tea has been demonstrated to contain characteristic compounds, such as
caffeine, catechins and theanine (Table 1.7). Only species of section Thea in the entire genus of
Camellia contain galloyled catechins such as (�)-epicatechin gallate (ECG) and (�)-epigal-
locatechin gallate (EGCG) and the non protein amino acid, theanine. Anthocyanin-rich tea
has also been described in Japan and Kenya (Terahara et al., 2001; Kerio et al., 2012). Eugenol
glycosides, sasanquin and fluorescent flavonoid sulfates have been used to study introgression
of C. japonica traits into C. sasanqua (Parks et al., 1981).
The IPGR descriptor list recognizes some chemical parameters in black processed tea as highly
discriminative. These include theaflavin and thearubigin contents and fractions, tea quality
type and the terpene index (TI). Leaf terpeniods have successfully been used to characterize
closely related Camellia species (Takeo, 1983; Nagata, 1986; Owuor et al., 1987) though at
higher levels of classification, they are less useful owing to convergence and reticulate evolu-
tion. Owuor et al. (1987) used the terpene index (TI) to distinguish between some Kenyan tea
clones. Though some overlap was noted, it was established that the Assam types had TI close to
1.0 while the China types had TI near zero. Although Hazarika and Mahanta (1984) charac-
terized Assam, China and Cambod tea based on variations in chlorophylls a and b and four
carotenoids (neoxanthine, violaxanthine, B-carotene and lutein), these characteristics were
unstable and varied with season, making them ineffective in large-scale systematic studies of
tea. Magoma et al. (2000) used the ratio of dihydroxylated to trihydroxylated catechins to
delineate different varieties of tea. Studies of this nature are important to establish the affinities
of hybrids to the major taxonomic categories.
Total tannin content and caffeine have also been used to discriminate tea clones (Takeda,
1994). In a study comparing tea germplasm from India, Bangladesh, Sri Lanka, Taiwan,
China and Japan, Takeda (1994) found that the Japanese and Chinese germplasm were low
in their total tannin content and caffeine content. Studies in Kenya have also revealed the
Japanese tea as low in total polyphenols when compared to Kenyan germplasm (Wachira and
Kamunya, 2005b). In Japan, low-tannin-content cultivars are selected for production of
green tea. In Kenya, tannin and caffeine profiles have been widely usedto characterize the
Kenyan tea germplasm. Wide variations in tannin and caffeine content have been observed in
the Kenyan tea germplasm (Table 1.8). Further, tea cultivars can also be classified based on
their capacity to undergo auto-oxidation as a consequence of different polyphenol oxidase
(PPO) activity. In Kenya, a non-fermenting (PPO-deficient) tea plant has been selected
(personal observation).
MOLECULAR MARKERS
The emergence of molecular techniques has provided a rapid and efficient means of exam-
ining accumulated genetic differences in the tea gene pool without interference of the
environment. Molecular markers have provided an important set of descriptors which are
able to differentiate between genotypes, variety types and even different species of the genus
Camellia. These markers are highly discriminative and can even distinguish genotypes that
cannot be distinguished using morphological traits. They are useful for the determination of
differentiation and relatedness within cultivated tea. In a study that profiled three NADP-
linked dehydrogenase isozymes, Magoma et al. (2003) revealed that tea clones could be
accurately partitioned according to their phylogenetic origins. The development of DNA
markers has further improved the ability to identify tea clones in commercial use and more
so those used as breeding stocks (Wachira et al., 1995; Paul et al., 1997; Wachira et al., 2001;
Singh and Ahuja, 2006). They also provide a measure for accumulated genetic variability
(Wachira et al., 2001). Molecular markers have also been demonstrated to be taxonomically
informative at the species and genus level. Phylogenetic relationships in Camellia which have
TABLE 1.7 Leaf Biochemicals in Plants from the Genus Camellia
Sample
Flavanol
Caf Thb Thea EC (D) C EGC ECG EGCG SQN
Section Thea
C. sinensis var. sinensis
C. sinensis var. assamica
C. taliensis
C. irrawadiensis
III
III
III
I
I
e
II
I
III
II
I
I
III
III
II
II
I
I
I
I
III
II
II
I
III
II
II
I
III
II
II
I
N.D.
N.D.
N.D.
N.D.
Section Camellia
C. japonica
C. japonica var. decumbens
C. saluenensis
C. pitardii
e
e
e
e
e
e
e
e
e
e
e
e
III
III
I
II
I
III
II
I
e
e
e
e
e
e
e
e
e
e
N.D.
N.D.
D.
D.
Section Heterogenea
C. furfuracea
C. granthamiana
e
e
e
e
e
e
e
e
e
e
e
e
e
e
e
e
N.D.
N.D.
Section Paracamellia
C. sasanqua
C. oleifera
C. kissi
e
e
I
e
e
e
e
e
e
I
e
e
e
e
e
e
e
e
e
e
e
e
e
e
D.
N.D.
N.D
Section Theopsis (5 species) e e e I e e e e D.
Section Camelliopsis (3 species) e e e e e e e e N.D
Interspecific hybrids
C. sinensis X C. japonica (3 clones)
C. japonica var. decumbens X C. sinensis
C. sasanqua X C. sinensis (4 clones)
II
II
III
e
I
I
I
I
II
III
III
III
I
III
I
III
III
II
II
III
II
III
III
II
N.D
N.D
D.
Dubiae
C. wabisuke
C. vernalis
C. hiemalis
C. tenuiflora
e
e
e
e
e
e
e
e
e
e
e
e
III
II
II
I
I
I
I
I
I
I
I
I
I
e
e
e
e
e
e
e
N.D.
D.
D.
N.D.
Caf, caffeine; Thb, theobromine; Thea, theanine; EC, (�)epicatechin; (þ)C, (þ)-catechin; EGC, (�)-epigallocatechin; ECG, (�)-epicatechin gallate; EGCG,
(�)-epigallocatechin gallate; SQN, sasanquin; e, <0.01%; I, 0.01e0.3%; II, 0.3e1.0%; III, >1.0%; N.D., not detected, D., detected. (After Nagata, 1986.)
CHAPTER 1
The Tea Plants: Botanical Aspects
13
been constructed using molecular data have been similar to those obtained using
morphological and biochemical affinities (Wachira et al., 1997). Molecular markers,
however, provide a greater degree of resolution. Moreover, molecular tools have been utilized
to generate genetic linkage maps of tea and to identify genes responsible for important
agronomic and biochemical traits (Matsumoto et al., 1994; Hackett et al., 2000; Kato et al.,
2000; Kaundun and Matsumoto, 2002; Chen et al., 2005a, b; Ma and Chen et al., 2006;
Kamunya et al., 2010).
TABLE 1.8 Summarized Data of Average Tannins Content in a Collection of Kenyan Tea
Clones
Tannin
Lowest (%)
W/W
Highest (%)
W/W
Epigallocatechin (EGC)
Epigallocatechin gallate (EGCG)
Epicatechin (EC)
Epicatechin gallate (ECG)
Caffeine
1.59
0.00
0.00
2.61
0.35
17.62
10.05
4.50
8.60
4.87
TABLE 1.9 Summary of Results of Crosses between Tea and Some Allied Species in the
Genus Camellia
Section Male Species Chromosome No. Cross Compatibility
Camellia C. japonica (30) Low
” C. hongkongensis (30) Impossible
” C. pitardii (30) Low
” C. saluensis (30) Low
Paracamellia C. brevistyla (30) Low
” C. kissi (30) High
” C. oleifera (90) Low
” C. sasanqua (90,60) Low
Camelliopsis C. assimilis (30) Moderate
” C. caudata (30) High
” C. salicifolia (30) Moderate
Theopsis C. cuspidata (30) High
” C. fraterna (90) Low
” C. lutchuensis (30) Impossible
” C. nokoensis (30) Moderate
” C. rosaeflora (90) Impossible
” C. transariensis e Low
” C. transnokoensis (90) Low
Thea C. irrawadiensis (30) High
” C. taliensis (30) High
Heterogenea C. furfuracea (30) Impossible
” C. granthamiana (60) Impossible
Corallina C. parviflora (e) ???
Dubiae C. drupifera (90) Low
” C. miyagii (90) Moderate
” C. tenuiflora (60) Low
With tea (C. sinensis) as female species. (Summary after Takeda, 1990.)
SECTION 1
Tea, Tea Drinking and Varieties
14
OTHERS
Cross Compatibility
Compatibility between species within the genus Camellia has been used to construct species
relationships (Takeda, 1990). Several Camellia species hybridize with tea (Table 1.9). The
relationships constructed from species affinities are however not useful for description of
individual tea varieties and clones.
SUMMARY POINTS
l Tea is classified in the subgeneric group Thea of the genus Camellia.
l Several members of the genus Camellia freely interbreed among themselves.
l The numerous interspecific hybrids between members of Camellia have complicated
taxonomy within the genus.
l The tea beverage is largely processed from Camellia sinensis ((L.) O. Kuntze).
l In China, several other species of Camellia are used to make tea-like beverages.
l Cultivated tea plants are largely differentiated by leaf morphophysiological traits.
l The three major cultivated forms of tea include the China variety (Camellia sinensis var.
sinensis (L.)); the Assam variety (Camellia sinensis var. assamica (Masters) Kitamura) and the
Cambod race (C. assamica ssp. Lasiocalyx (Panchon ex Watt)).
l The small-leafed China variety is predominantly cultivated in China and Japan for the
production of unaerated green tea, while the large-leafed Assam variety is cultivated in
India, Sri Lanka, Africa and Argentina for the production of aerated black tea.
CHAPTER 1
The Tea Plants: Botanical Aspects
l The three predominant varieties of tea differ in their morphological, physiological and leaf
biochemical traits as well as in their molecular profiles.
l New emerging consumer requirements may necessitate tea breeding for high or low
functional components, e.g. in catechins, flavanoids, theanine, caffeine, theobromine,
Gamma Amino Butyric Acid (GABA), b-carotene, astringency, aroma, etc.
15
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17
	1 - The Tea Plants: Botanical Aspects
	Introduction
	Classification in Camellia
	Methods of Distinguishing Types of Tea
	Morphological Traits
	Cytological markers
	Chemical/Biochemical Traits
	Molecular Markers
	Others
	Cross Compatibility
	Summary Points
	References