Improved transformation of alfalfa somatic embryos using a superbinary vector

Increased transformation efficiency of alfalfa (Medicago sativa L. cv. Zaječarska 83), was achieved using Agrobacterium tumefaciens LBA4404 carrying the superbinary vector pTOK233 and the hpt gene for hygromycin resistance. Evidence for transformation was based on GUS activity and the presence of a fragment of the uidA gene in transformed embryos and regenerated plants, as demonstrated by the polymerase chain reaction. Efficiency was 1% (LBA4404/pBI121) to 14% (LBA4404/pTOK233) higher than that of some other vectors used in previous work with the same cultivar. The higher efficiency may be due to the presence of an extra set of vir genes in pTOK233. Moreover, the presence of the hpt gene, enabling the use of hygromycin instead of kanamycin for selection, was better for the development of secondary somatic embryos, thus contributing to a higher final number of transgenic plants.