Genetic Modification of Soybean with a Novel Grafting Technique: Downregulating the FAD2-1 Gene Increases Oleic Acid Content

A hairpin RNA-encoding construct targeting gmFAD2-1 was transformed into soybean, and an optimised Agrobacterium-mediated embryonic tip system was employed. A novel intergeneric grafting method using transgenic plantlets as scions was used instead of the conventional rooting method. Compared with traditional acclimatisation, the survival ratio of cleft grafts increased by 70%, and the culture period was shortened by about 40 days. The regeneration frequency of the grafted shoots in this embryonic tip system was approximately 74.6%. Soybean transformants were confirmed by Southern and Northern blot hybridisation analyses. The fatty acid composition of the T-1 and T-2 seeds from the transformed plants was determined by gas chromatography. The resulting downregulation of the gmFAD2-1 gene substantially increased the level of oleic acid from 16% to 55% as indicated by the oleic desaturation proportion (ODP). The ratio of plants with high ODP, moderate ODP and low ODP was about 1:2:1, which was consistent with a single-gene segregation pattern.