Germplasm Preservation

Summary

There is a need for culture storage by both conventional and novel techniques in plant breeding and in the in vitro production of secondary compounds. Cultures can be stored by slow growth or cryopreservation. Slow growth is most successful for shoot cultures. Medium-term storage in increments of one or two years can be carried out for several species. Callus cultures are less amenable and there is evidence for progressive deterioration of some traits. Cryopreservation is the only sensible option for long-term storage. Suspension and callus cultures of many species can be cryopreserved. Results on recovery and stability are very encouraging. Embryo cultures show great promise but serious problems are encountered in the cryopreservation of shoot tips. Large differences in response are observed between species, and low survival levels are often compounded by disorganized development. To date, most cryopreservation research has involved an empirical approach but if further progress is to be made, a greater understanding needs to be gained of freezing injury and its control at the molecular, biochemical and cellular levels. In vitro conservation should be viewed as one of a range of complementary conservation strategies that range from conventional gene banking to the development of gene libraries.