Stable genetic transformation of high oleic Helianthus annuus L. genotypes with high efficiency

Two previously optimized procedures for genetic transformation of two economically important high oleic sunflower genotypes (H. annuus cv. capella and SWSR2 inbred line) were used to generate stably transformed sunflower plants of these genotypes expressing gus reporter gene: Agrobacterium tumefaciens-mediated gene transfer to juvenile split apical meristems was applied to cv. capella, and a biolistic gene transfer method using the same target tissue was applied to SWSR2 inbred line. Out of 120 originally used explants of cv. capella, five transgenic regenerants could be identified by biochemical and molecular analysis. Thus, transformation efficiency amounted to 4.1%. For SWSR2 inbred line, 125 explants were used and six transgenic regenerants could be identified in an identical manner, resulting in a transformation efficiency of 4.8%. The highest expression level of the gus gene resulted in a yield of recombinant protein of approx. 0.2% total soluble protein. Additionally, T1 progeny was tested for gus gene inheritance in both genotypes. From approx. 75% of the T0 plants, the gus gene was stably transmitted to the T1 progeny and expressed in a detectable amount. To test the reproducibility of the transformation procedures, they were used to introduce another reporter gene, mgf5, into both genotypes. The resulting transformation efficiencies were 3.3 for both genotypes. gfp proved to be a suitable reporter gene to select transgenic regenerants in early developing stages. The data presented here demonstrate for the first time the reproducible transformation of high oleic sunflower genotypes with high frequency.