An assay to measure the extent of variation in micropropagated plants of Begonia x hiemalis

The extent of somaclonal variation is usually assessed by determining the percentage of plants aberrant for a specific trait (e.g. phenotypical characteristics, chromosome number, electrophoresis pattern of proteins). We have assessed the extent of variation in micropropagated plants of Begonia x hiemalis cv. Schwabenland Red in another way. In three somaclonal populations the value of the standard deviation (SD) of a quantitative trait was determined, namely the SD of the natural logarithm of the ratio of the lengths of two leafribs (SD of In c/a). Plants, regenerated from callus, induced and maintained at a high concentration of 2,4-dichlorophenoxyacetic acid (2,4-D), had a significantly larger SD, whereas the mean was not affected at all. The observed increase of the SD is likely to have been caused by somaclonal variation, but epigenetic variation cannot be ruled out. It is concluded that differences in the values of the SD may be used to assess differences in the extent of variation.