Cryopreservation of Pelargonium shoot tips by encapsulation-dehydration:: Effects of sucrose concentration, dehydration duration and genotype

In order to guarantee safe, long-term conservation of the National Institute of Horticulture (I.N.H.) Pelargonium collection, meristem cryopreservation studies have been undertaken. Survival and regeneration were obtained on P. x peltatum 'Balcon Lilac' using an encapsulation-dehydration process involving apex preculture in a liquid medium progressively enriched with sucrose (up to 1M) prior to dehydration with silica gel. In order to simplify the process, apex tolerance to high sucrose concentrations was studied. Pelargonium apices were directly precultured for 48h in a liquid medium with sucrose concentrations from 0.088M to 1.25M. Up to 0.75M, 100% survival was obtained, and more than 60% survived at 1.25M. Cryopreservation, using a direct preculture with 0.75M sucrose, was then carried out. Survival rates as good as the ones obtained with progressive preculture were obtained (nearly 50%). This simplified process was tested on 14 genotypes representative of the diversity of our collection. Apex survival was obtained for each of them, but variability was observed. Survival rates were between 27.5% (P. x hortorum 'Renard Bleu') and 83.9% (P. x hortorum 'Bicolor'). Plants were obtained after cryopreservation for P. x grandiflorum 'Pansy' and P. x peltatum 'Balcon Lilac'. Studies should be continued in order to improve the regeneration rate on a large sample of genotypes and to try to understand the origin of cryopreservation tolerance variability according to genotype.