Abstract:
Oil palm (Elaeis guineensis) is a globally important vegetable oil crop, contributing over 35%
of the world’s oil supply due to its superior oil yield per hectare. To fulfil the global demand
for high-quality planting materials, hybrid seeds are not optimal due to their genetic variability.
Induction of somatic embryogenesis in floral explants enables mass clonal multiplication of
elite genotypes. However, the collection of early inflorescence stages causes significant damage
to the palm; thus, exploring the potential of utilising the latter inflorescence developmental
stages is important. The effect of floral tissues extracted from different inflorescence developmental
stages (18–21; 17th inflorescence considered the most immature externally visible
stage) was tested against four concentrations of 2,4-dichlorophenoxyacetic acid (2,4-D; 0, 2, 5,
or 10 mg/L) using Murashige and Skoog (MS) medium in a two-factor factorial experiment on
direct formation of somatic embryoids under light at 28 ◦C. Forty samples were used for each
combination. Direct embryo formation and embryo diameter were recorded at three months
and analysed using analysis of variance (ANOVA). No interaction effect was found among the
tested factors. The inflorescence stage significantly impacted embryo formation and growth
(p < 0.0001). Stage 20 resulted in the maximum embryogenic potential with the highest average
number of embryoids (0.82±0.08) and the greatest embryo diameter (1.01±0.08 mm),
compared to the other stages. This could be attributed to the higher totipotency and responsiveness
of the mitotic cells present in the floral buds. The tested concentrations of 2,4-D did
not significantly impact embryo induction, but they did influence embryo growth. The embryo
diameter in the presence of 2 mg/L and 5 mg/L 2,4-D was comparable with the absence of the
growth regulator (p < 0.01), whereas the lowest size was recorded at the highest growth regulator
level, 10 mg/L. These results indicate that, within the tested range, the auxin concentration
is not significantly effective in embryogenic induction efficiency. This study emphasises the
importance of explant selection during the induction of somatic embryogenesis in oil palm and
provides insight toward enhancing an effective clonal propagation method.
