Clonal propagation amenability of selected elite (DxP) and clonal tenera ortets of oil palm (Elaeis guineensis Jacq.)

The scale up of high quality oil palm ramets production is a main priority for all commercial tissue culture laboratories. To date, oil palm cloning technology is generally inefficient with low embryogenesis rate, genotype dependency and insufficient elite ortets. As the trends in culture development for mass propagation remains unpredictable, a thorough investigation of the relevant process is immensely important. This study aims to evaluate and expound the performance of selected elite tenera ortets for large scale production specifically during the stages of callogenesis, embryogenesis and embryoids maintenance en route for enhanced oil palm yield. Leaf explants were cultured on Murashige and Skoog (1962) medium with the current standard production protocol. Clonal ortets yielded callus of 1,340 ± 149 lines significantly (F=7.46, P=0.014) which refers to the frequency of callus initiated from the edge of cultured immature leaflet explants at 0.52-fold higher compared to elite tenera (DxP) ortets at 698 ± 182 lines. Besides, clonal ortets demonstrated shorter callus induction time than elite tenera ortets. The earliest callus formation for clonal and elite tenera ortets were observed after 93.90 ± 4.27 days and 107.00 ± 7.11 days respectively (F=2.73, df=1, 18; P>0.05). Embryoid lines achieved were significantly higher (F=38.00, P=0.00) in clonal ortets (794 ± 108 lines) by 8.6-fold against elite tenera ortets (91.6 ± 35.0 lines). In addition to that, differences of the embryoid line production rapidity between ortet types were found to be statistically significant (F=5.71, df=1, 18: P<0.05) in which clonal ortets developed embryoids faster by an average of 68 days earlier than the elite tenera. Statistical analysis of the data showed that there was positive correlation (r=0.69449, P<0.05) between the total of embryoid lines formed with the total production of callus derived from elite tenera and clonal ortets throughout the production process. The embryoid lines are represented as the frequency of embryoid developed from the callus which were observed as whitish in colour and appear with smooth surface. This indicates that for both types of ortet, the initiation of embryoid is proportionate to the production of callus lines (r=0.69449, P<0.05). The growth models for describing polyembryoids (PE) development for clonal and elite tenera ortets versus time of subculture or pattern were established. Meanwhile, the growth rate pattern of elite tenera ortets appeared to be non-uniformed, or uncertainty in the culture growth development compared to the series of clonal ortets tested. The potential of ortets development therefore could be estimated from a logistic growth curve fitted through the PE culture growth (in weight, g) against the duration of week after the initial culture. The growth patterns of clonal ortets are observed to be more predictive which facilitate further growth prediction. Therefore, the clonal ortets offers the best source for oil palm propagation optimization towards upscaling the ramets production in commercial scales.

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