A two-stage pretreatment of seedlings improves adventitious shoot regeneration in sugar beet (Beta vulgaris L.)

The effects of a two-stage pretreatment of seedlings on the subsequent shoot regeneration capacity were investigated. Pretreated seedlings were obtained by germinating seeds on three different germination media and then further culturing on six different growth media. Lamina and petiole explants of two sugar beet (Betavulgaris L.) breeding lines were then excised from the pretreated seedlings and cultured on five different shoot regeneration media. In both breeding lines, petiole explants produced significantly more shoots than lamina explants with higher frequencies of organogenic capacities; petiole explants of the lines M1195 and ELK345 produced a mean of 2.1 and 2.7 shoots per explant while their lamina explants produced 1.5 and 2.2 shoots per explant, respectively. A genotypic variation was evident as the line ELK345 was more productive for shoot development from both types of explants. In overall comparisons of different germination, growth and regeneration media, germination medium was most effective when supplemented with 0.5 mg/l 6-benzyladenine (BA) while both growth and regeneration media were most productive when contained a combination of 0.25 mg/l BA and 0.10 mg/l indole-3-butyric acid (IBA). Of all the treatments tested, the highest mean number of shoots per explant (8.3 shoots) and frequency of organogenic explants (75.6%) were obtained on regeneration medium supplemented with 0.25 mg/l BA and 0.10 mg/l IBA when petiole explants of the line ELK345 were excised from the seedlings that had been germinated on medium containing 0.5 mg/l BA followed by further growth on medium containing 0.25 mg/l BA and 0.10 mg/l IBA.