Cryopreservation of Chrysanthemum morifolium (Dendranthema grandiflora Ramat.) using different approaches.

Chrysanthemum species are grown both as ornamentals and for the production of pyrethrum. Recent increased production and breeding efforts have raised the need for the conservation of valuable germplasm. Chrysanthemum has been cryopreserved by controlled-rate-freezing as early as 1990. We report here deep-freezing of shoot tips of C. morifolium var. Escort by different technical procedures: controlled-rate-freezing, encapsulation/dehydration, ultra-rapid-freezing by the droplet method and vitrification. While vitrification yielded the highest shoot regeneration rates, the very simple droplet method was also successful in this respect. Droplet freezing was successfully performed with nine cultivars. Our results open the door to the successful use of alternative methods if one method fails to cryopreserve a variety. Furthermore, it enables comparative investigations of genetic stability and cyro-injury to be carried out.

Recovery of potato apices after several years of storage in liquid nitrogen.

A method for the systematic cryopreservation of potato apices was developed by the Deutsche Sammlung von Mikroorganismen und Zellkulturen GmbH (DSMZ) and the Institute for Crop and Grassland Science of the Federal Agricultural Research Centre (FAL, Braunschweig). Designed specifically for routine use in genebanks, this method uses a very simple ultra-rapid freezing approach and was applied to a wide range of varieties within the Federal Centre for Breeding Research on Cultivated Plants (BAZ, Quedlinburg) Potato Collection. After several years of storage in liquid nitrogen, shoot tips from a random sample of 51 varieties were thawed and the survival and shoot regeneration percentages compared to those measured immediately after freezing. There were no major changes in either survival or recovery of frozen apices. Data presented are not the outcome of a systematic experiment but from that accumulated during our work from 1992 to 1999.

A novel encapsulation technique for the production of artificial seeds.

A novel technique for the encapsulation of plant material in calcium alginate hollow beads was tested. The technique involves suspending plant material (i.e. plant cells, tissues, organs, shoot tips, somatic embryos) in a solution containing carboxymethylcellulose and calcium chloride and then dripping it into a stirred sodium alginate solution. In initial experiments with Daucus carota (carrot), it was found that after 14 days of cultivation, 100 % of seeds encapsulated in calcium alginate hollow beads would germinate in the liquid core and that 13% would burst the capsules. Embryogenic calli developed inside hollow beads and formed somatic embryos while calli in conventional calcium alginate beads became detached from the beads early in development, and no somatic embryogenesis occurred. With Solanum tuberosum (potato), development of calli was observed in 50% of hollow beads. Eighty-one percent of shoot tips encapsulated in hollow beads sprouted and grew out of the capsules.