From somatic variation to variant plants: mechanisms and applications

Plants from cell cultures show a high incidence of mutation. The causes of somaclonal variation are unknown, but the genetic consequences have been analysed. A range of genetic events are responsible, including single base changes; altered gene copy number; altered expression of multigene families; chromosome fragment interchanges; and mobilisation of transposable elements. Recent applications of these phenomena are discussed in this paper, for example, in vitro selection, somaclonal variation for agronomic traits, and limited gene transfer from cultured sexual and somatic hybrids. Research is outlined attempting to use high frequency chromosomal interchanges in wheat cell cultures to introgress genes from alien chromosomes. Two examples are cereal cyst nematode resistance on a rye chromosome and barley yellow dwarf resistance on a Thinopyrum chromosome. Some presumptive introgressed lines show selfed and backcross segregations, suggesting that the resistance, but not other alien markers, is now on a wheat chromosome.Key words: somaclonal variation, introgression, somatic hybridization, chromosome rearrangement, in vitro selection.