Establishment of encapsulation-dehydration technique for in vitro fragmented explants of Rosa hybrida L. cv. Helmut Schmidt

This study was carried out to evaluate the encapsulation-dehydration technique on IFEs of Rosa hybrida L. cv.Helmut Schmidt. The survival of IFEs was first assessed based on the effects of four sucrose concentrations (0, 0.25, 0.5 and 0.75 M) at different durations (0, 24 and 48 hours). The IFEs were then encapsulated and osmoprotected on shaker at 110 rpm with various sucrose concentrations (0, 0.1, 0.5 and 0.75 M). Subsequently, encapsulated IFEs were dehydrated under laminar air flow during three different time periods (0, 3 and 6 hours) on oven sterilized 50 g silica gel. The encapsulated IFEs were plunged into liquid nitrogen for a minimum duration of 24 hour. Encapsulated IFEs were thawed at 40°C for 90 seconds and cultured on full- strength MS medium supplemented with 3% sucrose for a week in dark, a week in semi-light and an additional 1 week under full light exposure. IFEs were then evaluated for survival by 2,3,5-Triphenyltetrazolium Chloride assay at 490 nm. The best conditions for the encapsulation-dehydration of IFEs of Rosa hybrida L. cv. Helmut Schmidt was obtained when IFEs were precultured in 0.25 M sucrose for 24 hours, osmoprotected in 0.75 M sucrose and dehydrated for 3 hours. Histological analysis showed cryopreserved IFEs with intensely stained nucleus but with severely damaged membranes.