History of Research
History Of Research In Tea Clones
History of Tea Research Tea was first introduced in Kenya around 1904. The early introductions were brought into the country in form of seed. Being highly self-incompatible and predominantly out-crossing, tea tends to produce highly heterogeneous progenies. The early introductions were therefore highly variable forming the initial populations of mixed genotypes. Uniformity and stability in yield and quality of the mixed genotypes could not be maintained; hence this necessitated the search for more uniform high yielding tea cultivars.
Organized tea improvement started with the formation of Tea Research Institute of East Africa (TRIEA) in 1961, and later the Tea Research Foundation of Kenya in 1980 with a mandate for research on all aspects of tea. The department of Botany was given the mandate of plant improvement hence the development of elite planting cultivars through breeding and selection.
The first set of cultivars was released in 1964. The TRI has adopted a naming system that identifies selected plants by their pedigree (Stock numbers) and identity of the selected cultivar. The pedigrees are provided in a Stock book maintained at TRI and it is continuously updated as new introductions are made. For example, cultivar TRFK 6/8 is from Stock 6 that had 205 related seedling teas introduced at TRI in 1957 from Chamogonday Estate and 8 represents the eighth bush; identity of the selected cultivar.
The first phase of the tea improvement was done by mass selection among introduced seedling jats based on morphological characteristics. The initial selections were based on similarity to the Assam varieties, vigour, density of plucking points and shoot size. The cultivars selected for high yields, were compared mainly to seedling tea, and later cultivar TRFK 6/8 for black tea quality. Initially a cultivar was released when it had yields greater than TRFK 6/8 or with quality worse than TRFK 6/8 but better than seedling tea or a cultivar with better quality than TRFK 6/8 and yields greater by 175% the yield of seedling tea. Using these criteria, cultivars TRFK 6/8, TRFK 7/3, TRFK 7/9, TRFK 7/14, TRFK 11/4, TRFK 12/12, TRFK 12/19, TRFK 31/8, TRFK 31/11, TRFK 31/27, TRFK 31/28, TRFK 31/29, TRFK 54/40, TRFK 55/55, TRFK 55/56, TRFK 56/89, TRFK 100/5 and TRFK 108/82 were released.
The next phase thereafter involved breeding through hybridization of selected parental stocks, superior in certain attributes that they were selected for. The early stages of this phase involved evaluation of maternal half-sib progenies (i.e. only maternal parent was known) of selected parents with the second phase involving the evaluation of full-sib crosses (both maternal paternal parents known) of selected maternal parents. The stocks were initially selected for yield and quality compared to the seedling stocks and cultivar TRFK 6/8 but has since been diversified to include other desirable attributes with respect to the growth and management of tea. The half-sib selected cultivars with the progenitor maternal parent TRFK 6/8 are TRFK 303/35, TRFK 303/152, TRFK 303/156, TRFK 303/179, TRFK 303/186, TRFK 303/199, TRFK 303/216, TRFK 303/231, TRFK 303/259, TRFK 303/248, TRFK 303/352, TRFK 303/366, TRFK 303/388, TRFK 303/577, TRFK 303/745, TRFK 303/791, TRFK 303/978, TRFK 303/999, TRFK 303/1199, TRFK 347/314, TRFK 347/326, TRFK 347/336 and TRFK 347/573. The later phase involving selections from bi-c1onal full-sib progeny resulted in the release of cultivars TRFK 337/3, TRFK 337/138 and TRFK 338/13. The cultivars had been selected solely based on yield performance. Tea improvement efforts however, shifted emphasis towards developing cultivars with combined optimum yields and quality. These efforts resulted in introduction of Cambod (Camellia sinensis var. assamica sub spp. lasiocalyx) variety of tea, which has also been evaluated under the local environmental conditions. Two cultivars, TRFK 301/4 and TRFK 301/5, which exhibited comparable performance in yield and quality to the high yielding and high quality cultivars released by the TRFK were later released from commercial utilization. The release of these cultivars have increased variability in the cultivated Kenyan germplasm and enhanced the range of choices of varieties available to the farmer.
Currently, Kenya produces and exports over 96% of her tea as black teas (www.teaboard.or.ke). The tea is sold to the world market in bulk and hence is largely used for blending lower quality teas from other countries. Consequently, it fetches low prices and therefore depressed revenue for tea growers in particular and low foreign exchange for the country in general. Consequently, the status of the global tea market demands intensification of research in product diversification and development of specialty tea products as well as value addition of the same. Hence, the need to develop and avail new cultivars with a combination of unique agronomic and novel traits that will provide the requisite raw material for the appropriate product development.
The TRI tea improvement programme has adopted a strategic approach that is geared towards diversification and value addition of tea products for the domestic and international markets. In this respect, the TRI has embarked on development of new varieties that would be suitable for green, oolong, white, purple and black teas. This effort is geared towards contributing to the government’s vision 2030, targeting tea products diversification and value addition in order to enhance profitability of teas as well as to boost economic growth in the agricultural sector. In this respect, TRI released a purple tea variety, TRFK 306, from her rationalized tea breeding programme for commercial utilization targeting a unique and unprecedented tea product - anthocyanin-rich medicinal tea.
Anthocyanins are flavonoids which belong to a group of polyphenolic compounds that have a C6-C3-C6 configuration consisting of two aromatic rings linked by three carbons. The word anthocyanin is derived from two Greek words anthos, which means flower, and kyanos, which means dark blue, revealing their important characteristic as natural colorants. The anthocyanins absorb light intensely at visible wavelengths imparting colour such as orange, red, blue and purple to plant tissues including flowers, vegetables and fruits. As a result of their intense coloration, they are used as dyeing agents and food colorants but the use of these natural colorants is limited due to their stability to pH, light and temperature. Industrially, they are important as natural food colourings since colour is the most important attributes of food that is appreciated for its intrinsic and aesthetic value and as a basis for identification and quality judgement. Attractive foods are sought as pleasure giving while unattractive foods are avoided. There are eighteen naturally occurring anthocyanins that have been discovered but among these, six are the most common. These are: i) cyanidin, ii) peonidin, iii) delphinidin, iv) petunidin, v) pelargonidin, and vi) malvidin. In plants, anthocyanins occur in glycosylated forms. They are linked to sugars such as glucose, galactose, arabinose, rhamnose, xylose and fructose. The berry nectars (grapes, bilberries and blueberries) are some of the richest source of anthocyanins. Other crops are purple cabbage, carrots, banana bracts, apples and many other edible fruits and vegetables. In purple tea, the most prominent pigment is malvidin, which is also ubiquitous in red grapes.
Worldwide, the tea plant has received immense attention due to its proven pharmacological properties and moreover it is inexpensive and widely available. Tea contains polyphenolic compounds mainly catechins but of all the known catechins, EGCG has been found to be the most potent pharmacologically particularly in boosting immunity and curing cancer.