Determination of the most efficient target tissue and helium pressure for biolistic transformation of oil palm (Elaeis guineensis Jacq.)

An efficient genetic transformation system for oil palm using particle bombardment was established. The transformation was performed using the pCAMBIA 1302 DNA which contains the green fluorescent protein (mgfp5) reporter gene and the selectable marker hygromycin phosphotransferase (hph) gene. Oil palm explants were bombarded under the following conditions: rupture disk to macrocarrier distance, 11 mm; macrocarrier to target tissue, 90 mm and using 1 µm gold particles as microcarrier. Four different pressures of helium were tested with three types of target tissues (mature embryo, embryogenic callus and young seedlings). From the transformation efficiency, calli were much more efficiently transformed in the biolistic process compared with mature embryos and seedlings. A 100% transformation efficiency for DNA delivery into callus oil palm explants was obtained at 850 psi helium pressures, for embryos a maximum 81.8% efficiency required 850 psi and for seedlings a maximum 75.9% efficiency required 1,550 psi. Using a confocal laser scanning microscope, and appropriate filters to block out the red fluorescence of chlorophyll, expression of the GFP gene was observed in all three bombarded explant types by a bright-green fluorescence. The mgfp5 gene was still present more than 8 months after bombardment, hence it indicated the stability of transgene in those transformants.