The effectiveness of traditional methods for inducing genetic variation has greatly increased with the introduction of various techniques in vitro. The new methods of obtaining generative and somatic hybrids in vitro have resulted in a greater recombinant variation, exceeding the levels delimited hitherto by mating barriers. The potential for producing mutants has expanded due to the use of mutant somatic cells (brought in with the explant) as well as to the application of mutagens to individual cells and protoplasts, the haploid ones in particular. Two specific types of variation, i.e. somaclonal and gametoclonal variation, have proved to arise under the influence of various factors in tissue culture. However, the full application of these two types is inhibited to some extent by the constrains on the regeneration ability of plants in culture, on the possibility to select variants in vitro, and on the continuity of the resulting changes. Cultures in vitro also make it possible to introduce directional genetic changes through the application of molecular techniques.