An efficient protocol for the production of transgenic Alstroemeria plants via particle bombardment

Alstroemeria plants were transformed by using an improved particle-gun–mediated transformation system. Friable embryogenic callus (FEC) induced from the leaves with axil tissues of Alstroemeria plant was used as the target tissue. Also, FEC was transformed with the bar gene was used as a selectable marker. In the case of plasmid pAHC25, 7.5% of the twice-bombarded FEC clumps showed blue foci, whereas the clumps with single bombardment showed only 2.3%. Additionally, a 90° rotation with double bombardment led to a higher frequency (6 times) of luciferase gene expression in PBL9780 than the control treatment. After 8 weeks of bombardment, more than 60 independent transgenic lines were obtained for pAHC25 and nearly 150 independent transgenic lines were obtained for PBL9780, all of which were resistant to PPT and demonstrated either GUS or luciferase activity. Regarding effect of osmotic treatment (0.2 M mannitol) with 7 different periods, the highest transient gene expression was obtained in 8 h before and 16 h after transformation in both pAHC25 and PBL9780. Compared with the control, at least three times more GUS foci and photons were observed in this treatment. With respect to different combinations of mannitol and sorbitol with 8 h before and 16 h after transformation, high numbers of transient and stable transgene expressions were observed in both 0.2 M mannitol and 0.2 M sorbitol used in the osmotic pre-culture. This combination showed the highest transformation efficiency in both pAHC25 (8.5%) and PBL9780 (14.5%). In the control treatment, only 10% of the FEC clumps produced somatic embryos. However, by using 0.2 M mannitol and 0.2 M sorbitol, the frequency of somatic embryos increased to 36.5% (pAHC25) and 22.9% (PBL9780). Of the somatic embryos produced, at least 60% germinated. Approximately 100 somatic embryos from these 210 independent transgenic lines from 2 plasmids developed into shoots, which were then transferred to the greenhouse. PCR analysis confirmed the presence of the bar gene. This is the report on the production of transgenic Alstroemeria plants by using particle bombardment with a high efficiency, thereby providing a new alternative for the transferring of gene of interests in Alstroemeria in the breeding program in the future.