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 clones was released in 1964. The TRFK has adopted a naming system that identifies selected plants by their pedigree (stock numbers) and identity of the selected clone. The pedigrees are provided in a stock book maintained at TRFK and it is continuously updated as new introductions are made. For example, clone TRFK 6/8 is from stock 6 that had 205 seedling teas introduced at TRI in 1957 from Chamogonday Estate and 8 represents the identity of the selected clone (i.e. bush number 8).
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 clones selected for high yields, were compared mainly to seedling tea, and later clone TRFK 6/8 for quality. Initially a clone 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 clone with better quality than TRFK 6/8 and yields greater by 175% the yield of seedling tea. Using these criteria, clones 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 clone 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 clones 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-coloniall full-sib progeny resulted in the release of clones TRFK 337/3, TRFK 337/138 and TRFK 338/13. The clones had been selected solely based on yield performance. Tea improvement efforts however, shifted emphasis towards developing clones with combined optimum yields and quality and it is Introduced Cambod (Camellia sinensis var. assamica sub spp. lasiocalyx) variety of tea has also been evaluated under the local environmental conditions.
Two clones, TRFK 301/4 and TRFK 301/5 have shown comparable performance in yield and quality to the high yielding and high quality clones released by the TRFK. The release of these clones have increased variability in the cultivated Kenyan germplasm and enhanced the range of choices of varieties available to the farmer.