EX VITRO SHOOT-TIP GRAFTING FOR RESCUING HYBRID VITROPLANTS OF MANGO (MANGIFERA INDICA L.) DEVELOPED THROUGH EMBRYO CULTURE

In a breeding program in mango involving an intervarietal cross, cv. Amrapali was crossed with cv. Kerala Dwarf with the objective of incorporating the dwarfing character into ‘Amrapali’. As the rate of breeding success using conventional procedures is very low owing to heavy fruit-drop, the in vitro technique of hybrid embryo rescue was applied to salvage hybrids. Immature fruits of the cross were harvested at 6 weeks post-pollination (wpp) and embryos were excised out aseptically. These were cultured in vitro on modified MS medium under controlled environment. Hybrid plantlets developed in 8-12 weeks. When the plantlets were transferred to non-sterile conditions for hardening-off, these would not survive transplantation, resulting in 100% mortality, sooner or later. Therefore, an alternate strategy was applied wherein the slender, in vitro raised hybrid plantlets of ‘Alphonso’ × ‘Kerala Dwarf’ served as scion shoot-tip donors for ex-vitro shoot tip grafting (ex vitro STG) while etiolated, laggard seedlings of cv. Totapuri served as the rootstock. Graft union was successfully established in 67% of the hybrids in 4-6 weeks. Until now, tissue culture was being used for in vitro shoot-tip grafting. This is the first report of ex vitro shoot-tip grafting being used for rescuing hybrids developed in vitro through embryo culture in any crop.