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Camellia sinensis (L.) O.Kuntze – ‘China’ type
C. assamica (Masters) Wight – ‘Assam’ type
C. assamica spp. lasiocalyx (Planch ex Watt) Wight – ‘Cambod’
type.
Family
Theaceae (Syn. Camelliaceae)
Habit
‘China’ cultivar is a big shrub, 1-3 m tall with
many virgate stems arising from the base of the plant near the ground.
Leaf hard, thick and leathery. Marginal veins distinct.
‘Assam’ tea plant is a small tree, 10-15 m tall and possess
robust branch system. Leaves are light green, flat or semierect, thin
glossy and broadly elliptic with distinct marginal veins.
The ‘Cambod’ is a small fastigiate tree, 6-10 m tall with
several upright, almost equally developed branches; leaf is more or
less erect, glossy, broadly elliptic with intermediate leaf size between
C. sinensis and C. assamica.
It is an evergreen, small tree, about 9.15 m in height under natural
conditions and is maintained as a shrub to about 1.5 m by continuous
pruning cycles for commercial cultivation. It is a shade-loving plant
and develops more vigrously under limited shade than in exposed situations.
Soil should be deep, free draining and acidic (pH, 5.2 to 5.6) and free
from calcium carbonate or reactive calcium.
Status
All the three species are cultivated for commercial exploitation.
Cultivated as monoculture; one of the most important plantation crops
of India.
Relatives
Ornamentals and wild types
Camellia irrawadiensis, C. japonica, C. caudata, C. kissi, C. sasangua,
C. taliensis, C. gracilipes and C. publicosta
Importance of the Species
Among the plantation crops, tea occupies an important position in view
of the quantity and value of its export to various countries. Tea determines
the economy of many countries. Tea contributes annually US $ 1500 million
to the gross national product of our country which includes US $ 480
million by way of export earnings. Millions of workers, particularly
women are employed in the tea industry, especially for harvest.
Remarks
Most important cash crop of India; improvement in quality as well as
quantity is a needed to maintain its global share of market.
Area Under Cultivation
Among all tea producing countries of the world, India has the largest
acreage under the crop. Assam (55.4%), West Bengal (24.0%), Tamil Nadu
(9.3%) and Kerala (8.3%) are the major tea producing regions in the
country.
Tea is also grown in a comparatively low hecterage
in Karnataka (0.49%), Tripura (1.4%), Himachal Pradesh, Uttar Pradesh,
Sikkim, Bihar, Manipur, Orissa, Nagaland and Arunachal Pradesh. Of the
total registered area of 4,18,331 ha under the crop, north India accounts
for 3,42,789 ha while in south India, the area is 75,542 ha constituting
81.9% and 18.1%, respectively.
Area of Collection
Assam, Nilgiris, Almora, HP
Conventional and micropropagation. Physiological and biochemical studies
also rhizosphere microbiology.
Micropropagation
Well defined protocols for four UPASI released elite tea clones, UPASI-3,
UPASI-26, UPASI-27 and BSB-1 have been developed.
Somatic embryogenesis
Protocol is being evolved to induce somatic embryos from mature/immature
cotyledons of drought tolerant cultivars as sources of explant.
Callogenesis
Morphogenic potential of the callus derived from different explant sources
is being studied.
1) Nature of explant
Aperiodic shoots originating from pruned tea bush grown under field conditions
were used as explant sources. Nodal segments with resting axillary buds
were used as explants.
Mode of regeneration
In vitro rapid multiplication without intervening callus phase.
Media details
Media for initiation
1/2 MS + BAP 3 ppm
Multiplication
1/2 MS + BAP 5 ppm + Adenine sulphate 160 ppm
Shoot elongation
1/2 MS + BAP 5 ppm + GA3 5 ppm
Rooting
1/4 MS + IBA 3 ppm
Shooting/rooting rate
Shoot multiplication rate of 1:10 was obtained within 75 days
of inoculation. Elongation rate was sporadic and rooting was around
90% in 45 days.
Total number of plants produced
More than 1000
2) Nature of explant
Nodal explants, cotyledon segments (from mature and immature seeds.
Mode of regeneration
Multiple shoot formation, somatic embryogenesis.
Media details
MS + 10.0 µM BAP + 1.0 µM IBA (for
multiple shoot formation)
MS + 10.0 µM BAP + 1.0 µM NAA (for somatic embryogenesis)
For rooting microshoots were incubated in 1/3 MS + 175.0 mM BAP for
10 days and then transferred to hormone free 1/3 MS medium.
Shooting/rooting rate
About 125 shoots per 100 mg of initial tissue could be obtained
in 6 subcultures. 100% rooting.
Total number of plants produced
In culture around 10,000 shoots are growing in nursery and field, 500
plants are growing. Hundreds of rooted plants can be obtained easily.
Well rooted plantlets were transferred to plastic pots/polythene sleeves
containing 1:1 ratio of soil and sand mixture and hardened in the mist
chamber conditions.
Mist chamber conditions
Minimum temperature : 200C
Maximum temperature : 30 + 50C
Light : 400-600 µEm-2sec-1
Humidity: 80-90 % maintained through intermittent misting
Field evaluation
Field performance of TC plants in relation to vegetatively propagated
(VP) plants is being studied under various south Indian agro-climatic
conditions.
Two batches of TC and VP plants were planted during 1996 and 1997 at UPASI
Tea Research Institute, Valparai. In Nilgiris (high elevation tea district)
and Central Travancore (mid elevation tea district) one batch each of
TC & VP plants were planted in the year 1997 and 1998, respectively.
Established plants have been centred in May’99 to induce lateral
branches. Cultural operations for bringing up of young tea to bearing
are being carried out in both centres. A batch of tissue culture plants
were transferred to the field in both Nilgiri-Wynaad (Gudalur) and Wynaad
(Meppadi) during 1999.
In the Anamallais, regular harvesting and biomass recording is being carried
out. Physiological responses of TC and VP plants have been investigated
using infra red gas analyser and radiotracer technique. No significant
variation was observed between VP and TC plants in terms of photosynthetic
rate, stomatal conductance, evaporation rate and water use efficiency.
However, tea clones exhibited significant variations in these parameters.
TC plants exhibited significant variation in photosynthetic carbon assimilation
and partitioning of assimilates over VP plants. Though there was a marginal
variation in photosynthetic pigments like chlorophylls and carotenoids
of TC and VP plants, they are not statistically significant. Biochemical
constituents like polyphenols, catechins and amino acids contents were
determined in crop shoots periodically.
Field evaluation trials underway, yet to be commercialized. As far as
tea is concerned, micropropagation technology is not expected to replace
conventional vegetative propagation methodology because of the low cost
of production. But it can be considered as a valuable tool to propagate
the in vitro/ex vitro identified elite prototype when the explant is scarce.
Laboratory level protocol is being refined for commercial exploitation
to support the traditional method of propagation.
Field performance of tissue culture plants under different agroclimatic
conditions of South India is in progress. Based on the field performance
and fine tuning of the existing micropropagation technique, the technology
may be transferred to entrepreneurs for commercial exploitation.
Tea being a moderately recalcitrant plants, establishes poorly under in
vitro conditions. The following factors are causative agent for poor establishment.
- Though vegetative vigour of plant is revitalised,
its establishment is very poor because of its extensive vegetative age.
(perennial crop).
- Browning of the explants due to the polyphenols exudation.
- Contamination due to fungi and bacteria
- Systemic nature of the contaminants
- A comparatively slow growth rate in the nursery/green house.
- Responses of tissue culture plants against biotic/abiotic stress needs
to be studied.
- To multiply more number of plants from
different identified new releases/clones.
- Successful hardening.
- Impact of cultural management operations on performance of TC plants
in the field.
- Refinement of the existing protocol to improve the efficiency of regeneration
and success rate of lab to land study.
- Transfer of technology as per the requirement.
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