Immature embryo: A useful tool for oil palm (Elaeis guineensis Jacq.) genetic transformation studies

Abstract

Oil palm (Elaeis guineensis Jacq.) is the highest yielding
\noil-bearing crop. However, being a perennial crop, genetic improvement
\nof oil palm is extremely slow. Indeed, compared to other annual oil
\ncrops such as soybean and rapeseed, genetic manipulations remained less
\nimportant. Therefore, to remain competitive, oil palm growers and
\nbreeders need new and novel approaches. In this report, the potential
\nof immature embryos (IE) as a useful tool for oil palm genetic
\ntransformation studies was evaluated. It was evident that IEs were
\namenable to both direct and Agrobacterium-mediated gene transfer. Due
\nto the abundant supply of IE, optimization of biolistic and
\nAgrobacterium-mediated gene transfer into IEs were easily carried out.
\nTransient transformation frequencies were comparable to other plant
\nsystems reported, with as high as 97.4% recorded for biolistic and
\n64.4% for Agrobacterium-mediated gene transfer. Like most moncots, oil
\npalm tissues were less sensitive to kanamycin, geneticin and
\nchloramphenicol. Instead, both hygromycin and phosphinotrycin were
\ntoxic 20 mg/l, making both suitable candidates for selecting putative
\ntransformants. IEs were also more responsive to in vitro manipulations
\nas compared to other explants such as leaf and root tissues. Rapid in
\nvitro response to callusing and embryogenesis or rapid and highly
\nefficient direct germination resulted in a shorter culture period. This
\nwould minimize the production of abnormal clonal palms, which has been
\nassociated to chromosomal aberration due to prolonged time in culture.
\nIn addition, IEs also allows rapid and direct introduction of elite
\ngenes into breeding programs and in biclonal seed production.