Applicability of cleft grafting in breeding program of tea (Camellia sinensis (L.) O. Kuntze)

The technique of grafting in tea is being widely used in conversion of seed baries and rapid multiplication of new varieties. Of late the technique of cleft grafting has further been exploited by grafting scions of two desired clones on opposite sides of a single cleft made over a rootstock. The technique is termed as "Y" grafting and is successfully utilized to produce seeds of new biclonal seed stocks. This technique also has tremendous significance in tea hybridisation program. Even in the first year of grafting, the grafted scions could produce seeds and thereby reduced the time of seed setting by 4 years compared to the conventional method of seed bad establishment. Following the 'V' grafting technique, 5 combinations (TVI X TV2, TV13 x TVI7, TV14 X TV21, TV20 X Bj-19 and BJ-19 x S.3A/3) were completed at the end of 2003. Seeds were harvested in 2006 and progenies were transplanted in an RBD layout for Long Term Trial (LTT) in 2007.Another set of6 grafting combinations, viz. Sikkim 1 X TV1, St. 652 x J-200, Koom 29 x BJ-19, S.3A/3 x TVI , S.3A/3 x TV21, T 78 x HV 39 were completed in 2005 and seedlings were planted in LTT at the 4th year of grafting. Application of benzyl adenine purine (BAP) to the graft junction @ 5 ppm enhanced the process of healing by stimulating the callus formation at the graft junctions. In another set of experiment, nine different combinations of quality clones (Hatichungi-311 X S.3A/3, Hatichungi-311 X TV2, Hatichungi-311 X MM-120, Hatichungi-311 X J-250, S.3A/3 X MM120, S.3A/3 X J-250, J-250 X MM-120, TVI X C. Sasanqua, TVI X C. Sasanqua) were grafted in 2010. The "Y" grafted clones J-250 x HC-311 produced flower and fruit after 1'1 year of grafting. Synchronisation of flowering between the clones matched for pollination and fertilization. To assess the feasibility of this 'V' grafting technique in distant hybridisation program in tea, c. sasanqua was used as one of the scions over the root stock TV!. Grafting was not successful as scions of the C. sasnqua dried out within 2-3 weeks. To overcome the incompatibility barrier, "bridge grafting" technique could be attempted where the bridge material will be compatible for stock and scion and thus making the 'V' grafting technique in hybridization of tea economic, reliable and commercially ~iable.