Cryopreservation of shoot tips of Trichilia emetica, a tropical recalcitrant-seeded species.

This paper reports the successful cryopreservation of shoot tips of Trichilia emetica, a tropical tree species producing recalcitrant seeds. Preculture of shoot tips on MS medium with 0.7 M sucrose or with 0.3 M sucrose + 0.5 M glycerol followed by cryoprotection with a mixture of glycerol and DMSO or with PVS2 was crucial for successful recovery following cryostorage. Three cooling rates were applied to assess the effects on post-thaw regrowth of shoot tips. Slow cooling of the shoot tips (WC 1.24 g/g DW) precultured on medium with 0.3 M sucrose + 0.5 M glycerol and cryoprotected with PVS2 resulted in high shoot production (71 percent). Subsequent to relatively faster cooling, only 38 percent of the shoot tips developed shoots. Ultra-rapid cooling with PVS2 resulted in callus formation with 55 percent regrowth. We report one of the very few successful attempts to cryopreserve explants alternative to zygotic axes of tropical tree species producing recalcitrant seeds.