Efficient Agrobacterium-mediated transformation and recovery of transgenic fig (Ficus carica L.) plants

An efficient and reproducible system for regeneration and Agrobacterium-mediated transformation of the common fig (Ficus carica L.) cultivars Brown Turkey (fresh consumption) and Smyrna (dry consumption) was developed. Optimal shoot regeneration (up to 100%) was obtained on MS basal salt mixture supplemented with 100 mg l−1 myo-inositol, 1 mg l−1 thiamine HCl and addition of 2.0 mg l−1 thidiazuron (TDZ), 2 mg l−1 indole-3-butyric acid (IBA), 4% sucrose and 0.8% agar. Regeneration was highly dependent on the dorsoventral orientation of the explants. When explants were cultured with the adaxial surface up, 100% regeneration was achieved with more than five shoots per regenerating explant in both studied cultivars. In contrast, if leaves were placed with their abaxial side up, shoot regeneration took place, but still mostly from the adaxial surface. Leaf explants of in vitro propagated plants were co-cultivated with the disarmed Agrobacterium strain EHA105 harboring the plasmid pME504 that carried the uidA-intron and nptII genes. Transformation efficiencies were in a range of 1.7-10.0% for cv. Brown Turkey and 2.8-7.8% for Smyrna. The transgenic nature of the regenerated plants was confirmed by molecular analyses (PCR and Southern blot) as well as by GUS staining. Similar to regeneration, the orientation of the leaf surface during organogenesis was a key factor for successful transformation. Successful transformation of commercial fig cultivars provides a new promising tool for the introduction of foreign genes into transgenic fig cultivars. The regeneration and transformation methodologies described here may pave the way for transgenic varieties with improved agronomic characteristics, such as storability and disease resistance, and will provide a means for the production of foreign proteins in the edible parts of fig, leading to improved nutritional and/or pharmaceutical composition.