Breeding of Fruit and Plantation Crops

Tea

• Tea : Camellia sinensis
• Family : Camelliaceae (Theaceae)

• The genus comprises about 45 species of evergreen shrubs and trees in tropical and subtropical Asia. Botanist distinguished 3 distinct tea- producing taxa which were referred as jats.

• China type: (Camellia sinensis): China type grows as a shrub 1-3m high with erect branches. Two morphological forms are identified in this type, viz. macrophylla with broad and long leaves and parviflora with small narrow leaves. Plants are resistant to cold and adverse conditions but low yielding.
• Assam type (Camellia assamica): Assam type is a small tree growing up to 10-15 m adapted to tropical conditions. Two types are recognized, viz., Assam type with light green leaves giving higher yields of better quality tea and Manipuri type with dark green leaves, drought resistant but with poor yields and quality.
• Cambodean hybrid type (Camellia assamica ssp lasiocalyx): The cambod type is conical in appearance reaching a height of 6-10m. Leaves semi erect vary in size between China and Assam types. In most species particularly the commercial jats, diploid chromosome number is 2n = 30.

Research Stations Board working on tea cultivation and in India

1. UPASI = United Planters Association of Southern India, UPASI Tea Research Institute, Nirar Dam B.P.O, Valparai – 642 127, Dist: Coimbatore, TN.
2. TES - Tea Experiment Satation, Tocklai, Jorhat, Assam
3. Crop improvement

• From the very early days of tea cultivation in India, seeds were used for planting and it remained so far over 120 years. 1949: The use of vegetatively propagated plants was started in 1949 after the release of clones by Tocklai Experimental Station. Tea being a highly cross-pollinated crop, the seedling populations is highly heterogeneous and comprises a large number of genetically distinctive genotypes which can be grown in a range of agro climatic conditions. The genetic and phenotypic variability of seedlings is high.

Objectives of crop improvement in tea

• The final aim of tea breeding programme is to develop a high yielding tea of acceptable quality. Yielding capacity is based on the yield per unit area of bush surface which is dependent upon number of plucking points and the size of shoots. Hence the following characters are important in selection programmes and for developing superior clones of tea

1. Vigour of the bush: Select bushes which come into plucking quickly and give continuously high yields.
2. Adaptability: Adaptability to local environment including drought resistance for dry areas and frost resistance were required.
3. Resistance to pests and disease
4. Hairiness of terminal bud: It denotes high polyphenol content.
5. Stature: Spreading habit and tight plucking tables of bushes with ample leaves below the plucking table
6. Minimal tendency to produce dormant buds (Bhanjhi buds) and without tendency to flower.
7. Evenness of flush
8. Shoot and leaf features:Large heavy shoots with long internodes and without markedly erect leaves . (Because such leaves are more difficult to pick)
9. Leaf flexibility: Select bushes producing flexible leaves which are easier to roll and ferment easily and have good colour in the finished product giving an infusion of appropriate colour, aroma and astringency.
10. Suitability for vegetative propagation: Select bushes which have capacity to root easily from cuttings.

• New cultivars are selected from the existing seedling populations or by hybridization, polyploidy, mutation or genetic engineering. The genetic base of our tea plant population should be broad-based and, therefore, a policy of clone-seed-clone-seed cycle is preferred.

• North India: The Tocklai Experimental Station has so far released 29 TV series clones, over 130 TRA/garden series clones, 100 industry clones and 9 Tocklai biblical seed stocks.
• South India: For use in south India, the UPASI Tea Research Foundation Valpari, has released 28 clones, about a dozen estate selections and 5 biclonal seed stocks. The UPASI TRF has also developed 7 nursery graft combinations using high-yielding clones as scions and drought-hardy clones as rootstocks.