ABSTRACT
Germplasm represents all the different genotypes that could be used for improvement. Improvement is accomplished traditionally by making sexual crosses between individuals and then selecting plants with the desired characteristics such as disease or stress tolerance or resistance. This chapter describes germplasm preservation for crop species and emphasizes where and how in vitro culture and cryopreservation are used for efficient and effective management. It emphasizes cryopreservation of shoot tips. Seeds are classified as either being desiccation tolerant or desiccation sensitive. Desiccation-sensitive seeds are produced by aquatic species, large-seeded species, some species native to tropical areas, and some temperate zone species of trees. Pollen may also be used to store genes from crops. Pollen from many species is desiccation tolerant and exhibits storage characteristics similar to desiccation-tolerant seed. Rapid warming minimizes any destructive ice crystal growth or devitrification as the cellular mileau gains more thermal motion.
