Somaclonal Variation

Summary

Eukaryote genomes are in a dynamic state of flux. This is most apparent in higher plants under in vitro culture where the amount of variability generated is extensive. Genetic and molecular analysis is providing some understanding of the events which give rise to somaclonal variation. In maize, a new fully functional electrophoretic variant at the alcohol dehydrogenase locus has been found among somaclones and subsequently characterized as resulting from a single nucleotide substitution. In wheat, variants have been analysed which affect traits such as height and alcohol dehydrogenase synthesis, as well as complex gene loci involved in the synthesis of grain amylases. Somaclonal analysis in maize and alfalfa has shown that cell culture greatly enhances the activation of transposable elements. For plant improvement, the enhanced frequency of genomic rearrangements during culture provides a new option to introgress alien genes from wild relatives into domesticated crops, and may enable the products of ‘new’ types of mutational events to be recovered.