Optimization of Agrobacterium-mediated transformation of sunflower (Helianthus annuus L.) immature embryos

Sunflower is an important oilseed crop, however the genetic transformation of sunflower has been very challenging to date. In the present study, we describe a successful Agrobacterium-mediated transformation approach via somatic embryogenesis from immature zygotic embryos of sunflower. By optimizing the culture medium, we have achieved high efficiency (45.5%) of somatic embryogenesis with MS medium containing 0.4 mg/l 2,4-D and 120 g/l sucrose when embryo size was less than 2mm. Agrobacterium tumefaciens LBA4404 harboring pGBI121-LycB was transformed into 1500 immature sunflower embryos derived from 4 different genotypes. Four strains of transgenic plants were obtain through kanamycin screening and subsequent validation via PCR and Southern Blot confirmed 3 positive strains, in which the transgenes were integrated into the genome of sunflower.