Tissue Culture of Oil Palm: Finding the Balance Between Mass Propagation and Somaclonal Variation
Abstract : The oil palm (Elaeis guineensis Jacq.) is typically propagated in vitro
by indirect somatic embryogenesis, a process in which somatic cells of
an explant of choice are, via an intermediate phase of callus growth,
induced to differentiate into somatic embryos. The architecture of the
oil palm, lacking axillary shoots, does not allow for vegetative
propagation. Therefore, somatic embryogenesis is the only alternative to
seed propagation, which is hampered by long germination times and low
germination rates, for the production of planting material. The current
oil palm somatic embryogenesis procedure is associated with several
difficulties, which are described in this review. The limited
availability of explants, combined with low somatic embryo initiation
and regeneration rates, necessitate the proliferation of embryogenic
structures, increasing the risk for somaclonal variants such as the
mantled phenotype. Several ways to improve the efficiency of the tissue
culture method and to reduce the risk of somaclonal variation are
described. These include the use of alternative explants and propagation
techniques, the introduction of specific embryo maturation treatments
and the detection of the mantled abnormality in an early stage. These
methods have not yet been fully explored and provide interesting
research field for the future. The development of an efficient oil palm
micropropagation protocol is needed to keep up with the increasing
demand for palm oil in a sustainable way. Mass production of selected,
high-yielding palms by tissue culture could raise yields on existing
plantations, reducing the need for further expansion of the cultivated
area, which is often associated with negative environmental impacts.
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