dual role of carbenicillin in shoot regeneration and somatic embryogenesis of horseradish (Armoracia rusticana) in vitro

Carbenicillin, a well-known antibiotic, has been reported to have growth regulator-like activity in vitro for some plant species. In the present paper we add horseradish (Armoracia rusticana) to the list of plants exhibiting such responses. This project began as an effort to eliminate latent bacterial contamination among established in vitro horseradish plants. Carbenicillin (100 mg L⁻¹) added to regeneration medium eliminated all visible bacterial contaminants. Unexpectedly, carbenicillin-grown explants regenerated adventitious shoots faster (14 days) than those on control medium (21 days). In addition eight of 11 horseradish cultivars grown on carbenicillin produced more adventitious shoots per explant than control. At much higher levels (2,000 mg L⁻¹) carbenicillin was found to retard somatic embryogenic callus induction. Based on these observations we suggest that carbenicillin at moderate levels enhances shoot development in horseradish. The mode of action of carbenicillin's growth regulator-like activity needs to be investigated.