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Ooi S.-E.,Malaysian Palm Oil Board | Choo C.-N.,Advanced Agriecological Research Sdn Bhd | Zamzuri I.,Malaysian Palm Oil Board | Ong-Abdullah M.,Malaysian Palm Oil Board
Journal of Oil Palm Research | Year: 2013

The in vitro propagation of the oil palm involves an indirect somatic embryogenesis process through an intervening callogenesis phase. Both processes are determining factors in the success of clonal propagation. This study aims to discover expression markers associated with hormone response as a means to measure the favourable response of oil palms to callogenesis. Expression levels of hormone responsive genes in cultured and uncultured leaf explants were measured by using quantitative real time PCR, followed by statistical analysis to determine whether a relationship to callogenesis existed. The potential for callogenesis in cultured leaf explants of oil palms was significantly correlated to the expression changes of a putative brassinosteroid leucine-rich repeat (LRR) receptor kinase (EgBrRK), a putative cytokinin dehydrogenase (EgCKX) and a putative response regulator type A gene (EgRR1). A regression model for callogenesis incorporating these three genes indicated a predicted R2 value of 67.89%. The larger reduction in the expression of EgRR1 and another cytokinin responsive gene, EgCK REGULATED KINASE, in cultures exhibiting higher callogenesis rates suggested an increase in cytokinin signaling output and cytokinin levels. This inference was supported by a slight decrease in the expression of EgCKX, suggesting a mild reduction in cytokinin degradation in these cultures. The use of these markers for the prediction of callogenesis rate in uncultured and one-day cultured leaf explants, may provide an early assessment of the callogenesis potential of oil palms.

Ping L.Y.,University Putra Malaysia | Boon Sung C.T.,University Putra Malaysia | Joo G.K.,Advanced Agriecological Research Sdn Bhd | Moradi A.,University Putra Malaysia
Malaysian Journal of Soil Science | Year: 2012

In order to reduce soil erosion on sloping lands, empty fruit bunches (EFB), Ecomat, oil palm frond heaps, or silt pit have been used by major oil palm plantations. Studies have shown that at 0-15 cm soil depth, organic matter content in EFB is highest among the four treatments. Besides, EFB had the highest humic acid content compared to the others, about two times higher than control. Our analysis showed that aggregate stability of EFB was the highest among four treatments at 54.88%, followed by Ecomat (47.7%), silt pit (44.76%) and finally, control (42.12%). We observed that organic matter content inversely correlated with Fe (p < 0.05) and Al (p < 0.05) oxides. Finally, yield of humic acids correlated with soil pH (p < 0.05), aggregate stability (p < 0.01) and aggregate size distribution (p < 0.01). Among the four treatments, application of EFB as a mulching material commonly practised in oil palm estates was found to be the best practice on sloping lands due to its high organic matter and humic substances content that retain soil particles by improving soil aggregate stability and aggregation.

Ooi S.-E.,Malaysian Palm Oil Board | Choo C.-N.,Advanced Agriecological Research Sdn Bhd | Ishak Z.,Malaysian Palm Oil Board | Ong-Abdullah M.,Malaysian Palm Oil Board
Plant Cell, Tissue and Organ Culture | Year: 2012

This study correlates the potential for somatic embryogenesis in cultured leaf explants of oil palm trees with changes in the expression of hormone-responsive genes. The results show that expression of the putative Aux/IAA gene EgIAA9 is specifically correlated to somatic embryogenesis. A regression model for embryogenesis indicated a predictive R 2 value of 63.55 % for this expression marker. Auxin is the plant growth regulator used for induction during the early stages of oil palm tissue culture. Expression of EgIAA9 decreased in response to increasing concentrations of exogenous 2,4-D. EgIAA9 expression profiles in cultured leaf explants from highly embryogenic palms, in embryogenic and non-embryogenic calli, and in response to increasing exogenous 2,4-D, suggested that endogenous auxin levels may be greater in highly embryogenic palms. The use of this marker to predict embryogenesis in oil palm tissue culture prior to the visible onset of this event is promising. Moreover, the results of this study prompt further investigations into the role of Aux/IAA genes in oil palm somatic embryogenesis. © 2012 Springer Science+Business Media B.V.

Hoang K.P.,Vietnam National University, Hanoi | Teo T.M.,Advanced Agriecological Research Sdn Bhd | Ho T.X.,University of Arkansas | Le V.S.,Vietnam National University, Hanoi
Parasites and Vectors | Year: 2016

Background: More effective mosquito control strategies are urgently required due to the increasing prevalence of insecticide resistance. The sterile insect technique (SIT) and the release of insects carrying a dominant lethal allele (RIDL) are two proposed methods for environmentally-friendly, species-targeted population control. These methods may be more suitable for developing countries if producers reduce the cost of rearing insects. The cost of control programs could be reduced by producing all-male mosquito populations to circumvent the isolation of females before release without reducing male mating competitiveness caused by transgenes. Results: An RNAi construct targeting the RNA recognition motif of the Aedes aegypti transformer-2 (tra-2) gene does not trigger female-to-male sex conversion as commonly observed among dipterous insects. Instead, homozygous insects show greater mortality among m-chromosome-bearing sperm and mm zygotes, yielding up to 100 males in the subsequent generations. The performance of transgenic males was not significantly different to wild-type males in narrow-cage competitive mating experiments. Conclusion: Our data provide preliminary evidence that the knockdown of Ae. aegypti tra-2 gene expression causes segregation distortion acting at the level of gametic function, which is reinforced by sex-specific zygotic lethality. This finding could promote the development of new synthetic sex distorter systems for the production of genetic sexing mosquito strains. © 2016 Hoang et al.

Melling L.,Tropical Peat Research Laboratory Unit | Yun Tan C.S.,University Technology of MARA | Goh K.J.,Advanced Agriecological Research Sdn Bhd | Hatano R.,Hokkaido University
Journal of Oil Palm Research | Year: 2013

The partitioning of soil respiration (SR) to root respiration (RR) and microbial respiration (MR) was conducted using the root exclusion and closed chamber method in three ecosystems on tropical peatlands. RR was estimated by differencing SR and MR. The forest ecosystem displayed significantly higher monthly MR compared with oil palm and sago ecosystems with the highest value of 219 mg CO2 C m-2 hr-1 in May 2003. This might be attributed to its thick leaf litter and root mat, and water filled pore space which was conducive for microbial activity. The lowest range of MR, between 153 mg CO2 C m-2 hr-1 (October) and 34 mg CO 2 C m-2 hr-1 (September), was found in the sago ecosystem probably due to its high water-table. The highest RR was recorded in the forest (172 mg CO2 C m-2 hr-1), followed by oil palm (128 mg CO2 C m-2 hr-1) and sago (95 mg CO2 C m-2 hr-1). The latter might be ascribed to its slow growth rate, while the former to higher root biomass and growth rate. The annual ratio of RR to SR was 52% in the sago ecosystem and 60% to 62% in both oil palm and forest ecosystems.

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