Successful Micropropagation of the Cadmium Hyperaccumulator Viola Baoshanensis (Violaceae)

Abstract

Viola baoshanensis is one of the most rare cadmium (Cd) hyperaccumulators, however, it is hard to propagate. Micropropagation has been applied to solve the problems with propagation of a few heavy metal hyperaccumulators. Therefore there is a high likelihood that micropropagation may offer a suitable method for large-scale propagation of V. baoshanensis. To test this hypothesis, three types of explants were used for shoot regeneration and various combinations of four plant growth regulators were used to improve shoot regeneration efficiency from leaflet of V. baoshanensis. Best shoot regeneration efficiency was obtained by incubating leaflet in a 1/2 MS medium supplemented with 2.5 μM BA + 2.5 μM IBA, therein shoot regeneration rate was 70.9% and the number of shoots formation per explant was 22.4. Rooting was achieved from almost all regenerated shoot growing on 1/2 MS medium without plant growth regulator. Micropropagated seedlings were acclimatized under greenhouse conditions and 95% of them survived and showed no visible morphological variation compared to their donor plant. Furthermore, there were no significant differences between regenerated and seed-germinated V. baoshanensis in Cd tolerance and accumulation. These results suggested that an efficient and rapid micropropogation system was successfully developed for V. baoshanensis.

KEY WORDS:

• cadmium
• hyperaccumulation
• leaf explants
• rapid propagation
• tissue culture

ACKNOWLEDGMENTS

This study was supported by the National 863 project of China (2006AA06Z359), Natural Science Foundation of China (40471117 and 30400053) and Team Work Project of the Natural Science Foundation of Guangdong Province (06202438).