Selection of transgenic flax plants is facilitated by spectinomycin

Regeneration of transformed flax shoots after inoculation with Agrobacterium tumefaciens carrying a binary vector with either a neomycin phosphotransferase (nptII) gene and a beta-glucuronidase (GUS) reporter gene or a spectinomycin resistance gene was examined. Hypocotyls from 4-day-old seedlings were inoculated with either of the two A. tumefaciens strains. Selection and regeneration were achieved on a medium containing 0.1 mu M thidiazuron, 0.01 mu M napthalene acetic acid 100 mg l(-1) kanamycin sulphate or spectinomycin sulphate and 300 mg l(-1) cefotaxime. Use of different neomycins for the selection of transformed tissues did select transformed calli but not transformed shoots either directly or via a callus phase. Selection based on spectinomycin resistance allowed the growth of transformed shoots. Transgenic shoots were rooted on a medium containing 100 mg l(-1) spectinomycin sulphate. Integration of the spectinomycin resistance gene into the flax genome was confirmed by Southern blot hybridizations and spectinomycin resistance was shown to be inherited as a dominant Mendelian trait. Therefore, spectinomycin resistance is more suitable for genetic engineering of flax than aminoglycoside resistance.