Generation of chlorsulfuron-resistant transgenic garlic plants (Allium sativum L.) by particle bombardment

We established an effective biolistic transformation procedure for transferring foreign genes into garlic (Allium sativum L.), which we demonstrated by generating transgenic plants resistant to chlorsulfuron, a sulfonylurea herbicide. We subcultured callus tissue from the apical meristem of garlic cloves and repeatedly selected calli with brittle, non-mucilaginous surfaces for over six months, to increase transformation efficiency. We then constructed recombinant DNA that contained the acetolactate synthase (ALS) gene from a chlorsulfuron-resistant Arabidopsis mutant, the cauliflower mosaic virus 35S promoter, the β-glucuronidase (GUS) reporter gene, and the hygromycin phosphotransferase (HPT) selectable marker gene. The garlic calli were bombarded twice with tungsten particles coated with the DNA constructs. Transformed calli were efficiently selected by embedding them in solid agar medium containing 50 mg 1^-1 hygromycin B. Selected propagules were regenerated into 12 independent plants. We confirmed that the transgenes were integrated and expressed in the plants using PCR-Southern and Northern blot analyses and by β-glucuronidase expression assay for GUS. The regenerated plants survived in the presence of 3 mg 1^-1 chlorsulfuron, demonstrating that their ALS was insensitive to this herbicide. These results illustrate the successful transformation of foreign genes into garlic plants. The set of procedures developed in this study is applicable to the generation of transgenic garlic plants with other agronomically beneficial traits.