Induction of variability in chimeric Aster cordifolius 'White Elegans' through somaclonal variation.

A protocol was developed for plant regeneration from leaf explants (lamina and petiole) of Aster cordifolius cultivar 'White Elegans', which is chimeric for chromosome number and the ligulate flower colour. Explants were cultured on MS or Gamborg's B5 medium in presence of IAA, 2,4-D and BAP, alone or in combination. The highest frequency of shoot regeneration was obtained on B5 medium supplemented with 2,4-D (0.09 mg l-1) and BAP (1.8 mg l-1). After the in vitro rooting stage and acclimatization, 90% of plantlets survived in the greenhouse. The regeneration process occurred by indirect organogenesis as shown by cyto-histology. The regenerants maintained the original chimerism for chromosome number. Pink flowers instead of the expected white ones were obtained in all regenerants. A hypothesis for the uniform colour change is discussed. Variations were detected in the regenerant generation (R0) for quantitative characters such as capitulum and disc diameters, and number of ligulate flowers. Since Aster can be vegetatively propagated, selection of variants in R0 can provide interesting material for breeding purposes.