Source Year: 1998

Two cryopreservation protocols, one using a classical freezing process and the other a simplified freezing process, were developed for embryogenic calluses of a commercial clone of Hevea, PR107. After preculture with 1 M sucrose and 10;dimethyl sulfoxide, embryogenic calluses were frozen in a programmable freezer at 0.2 degree C min-1 down to -40 degree C, or in a simple device consisting of an isopropanol bath enclosed in a polystyrene box, placed in a -80 degree C deep-freezer, thus achieving an average cooling rate of 0.2 degree C min-1 down to -40 degree C. High survival and rapid regrowth, as well as production of somatic embryos, were obtained with calluses cryopreserved using both freezing protocols. The simple freezing protocols was successfully used with a second commercial clone.