Effect of genotype, embryo maturity and culture medium on in vitro embryo germination of Sri Lankan coconut (Cocos nucifera L.) varieties

Poor in vitro germination of embryos of exotic varieties was reported as one of the major constraints faced during coconut germplasm exchange programmes. In this study, the effect of genotype, embryo maturity and culture medium on in vitro germination of coconut embryos was investigated. A significant effect (p < 0.05) of genotype on in vitro germination was observed between the selected cultivars, San Ramon Tall (SNRT) (77.48 %), Sri Lanka Red Dwarf (SLRD) (67.28 %), Sri Lanka Green Dwarf (PGD) (71.85 %) and King Coconut (RTB) (52.5 %). Embryo germination percentages were improved in solid media (91.66 % and 92.22 % in 75 g/L and 60 g/L sucrose respectively, p < 0.05) than in liquid media (56.66 % and 60.46 % in 75 g/L and 60 g/L sucrose, respectively) and the sucrose concentration has no effect on germination of SLRD embryos. Furthermore, maturity of the nut significantly affected the germination (p < 0.05) of embryos of PGD and the highest in vitro embryo germination was achieved by culturing embryos of the 12 month old bunch (97.67 %), while the lowest was observed in the 10 month old bunch (52.17 %). Addition of growth hormones favoured root growth of in vitro raised SLRD plants with a significant increase in the number of primary roots and the number of leaves (p < 0.05) when 10 μM BAP, 10 μM Kinetin and 200 μM NAA were added to the embryo culture medium.