The second group of planting materials recommended for commercial planting is the clonal seeds. Clonal seed varieties are essentially the hybrid seeds of F1 generation produced by natural hybridisation of two or more selected clones under natural condition. When two clones are involved, it is called biclonal seed variety, and if more than that, it is called polyclonal seed variety.
Tocklai Experimental Station, Assam, India has so far developed 14 biclonal (lebelled TS) and one polyclonal seed variety using the technique of line breeding and hybridization. The polyclonal seed variety, TS 203 involving seven clones (Gaurisankar) was released for Darjeeling. However, due to its unpredictable performance, this was discontinued for planting. Now, only the bi-clonal seed varieties are recommended for commercial planting. A few popular biclonal seed stocks are TS 397, TS 449, TS 450, TS 462, TS 506, TS 589 etc.
The UPASI Tea Research Foundation, Tamil Nadu has released five biclonal seed stocks viz., UPASI: BSS-1 to UPASI: BSS-5 characterised by drought tolerance and high yield potential. Superior genotypes with high yield, drought tolerance and superior quality characters have been used as male and female parents for production of these biclonal seed stocks. In addition the Research and Development Department of Tata Tea Ltd., Kerala, India has developed several biclonal seed stocks such as TTSS-1, TTSS- 2.
In other countries also clonal seeds stock varieties have been developed. Hybridisation between clones was initiated at Bangaldesh Tea Research Institute at the late sixties of the last centuary with a view to develop biclonal seed stocks combining the desirable characters present in different clones and have been released a few biclonal seed stock varieties like BTS 1 to BTS 4.
In Georgia, a good number of seed varieties having high yield and superior cup quality have been developed by polycross breeding between China and Cambod races. All the newly-bred varieties are frost resistant and some of these like Gerogian hybrid No.8 are said to thrive even at -220C.
In Kenya priority has now been shifted from selection of vegetative clones to production of biclonal seed primarily for want of reliable selection criteria for clones.