PROTOPLASTS AND SOMATIC HYBRIDIZATION

In a series of studies during the early 1960s, Cocking (1960, 2000; see Vasil 1976; Giles 1983) described methods for the isolation of plant protoplasts by incubating segments of roots and other tissues in crude mixtures of cell wall hydrolyzing enzymes. The small number of protoplasts that were isolated were used mostly for physiological studies. Two key developments in 1970 and 1971 pointed to the potential use of protoplasts for plant improvement: (i) Induced fusion of protoplasts of diverse species (Power et al. 1970) as a means to produce somatic hybrid cells and novel hybrid plants without regard to taxonomic relationships. (ii) The regeneration of plants from cultured protoplasts (Takebe et al. 1971). Plants can now be regenerated from protoplasts of a wide range of species. Similarly, a variety of somatic hybrids have been obtained between related as well as unrelated species, although useful hybrids have been produced only in a limited number of species, such as Brassica, Citrus and Solanum. Protoplasts have, however, proven to be very useful in genetic transformation of plants (Marton et al. 1979; Davey et al. 1980; Paszkowski et al. 1984), including the economically important cereals (Vasil and Vasil 1992).
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