Cryopreservation of Plant Cell, Tissue, and Organ Culture for the Conservation of Germplasm and Biodiversity

Abstract

The indiscriminate clearing of forests and agricultural land has led to the depeletion of the naturally occurring reservoirs of plant germplasm. About 20 000 species of higher plants are believed to be endangered, rare, and threatened with extinction. Moreover, the green revolution no longer appears to be green, as many of the original native cultivars, especially those of wheat, have been discarded and eventually lost. In Greece, for instance, since World War II, 95% of the wheat varieties have been abandoned (Plucknett et al. 1983), and some of them must have been lost, leading to a continuous depletion of genetic variability. On the other hand, the importance of conservation of rice germplasm has been adequately emphasized (Chang and Vaughan 1991), as wild relatives of rice are also disappearing because of various developmental projects. In maize, for instance, the damage caused by Helminthosporium maydis in the 1970s in the USA alerted plant breeders to look for unconventional sources of genetic variability to avoid such an eventuality in the future. The germplasm of a number of medicinal plants and forest trees is also threatened with extinction (Hussain 1983; Sakai 1986).