Isolation and Characterization of Potential Markers for Prolific Explant Tissues of Oil Palm (Elaeis Guineensis Jacq.)

Tissue culture is a promising technology for the mass propagation of elite oil palm. Although this approach has been widely used in the local oil palm plantation companies, the callogenesis and embryogenesis rates remain low. Therefore, the application of markers for early diagnosis of embryogenic potential would help in reducing the cost for tissue culture of oil palm. The first part of this study was aimed to identify DNA markers for oil palm prolific explant tissues via representational difference analysis (RDA), a technique whereby the differences between two highly related genomes can be identified. In this part, a total of five forward and reverse RDA were performed using the explant tissues possessing different proliferation ability; measurement was based on the previous tissue culture data of respective oil palm tissue culture agencies. Among the difference products identified, 13:14 C58 which was putatively enriched in non-prolific tissues, possesses a few nucleotide differences when aligned with the equivalent DNA region of the highly prolific tissues. However, further verification is needed to confirm its ability as a marker for distinguishing the non-prolific explant tissues from the highly prolific explant tissues. The second part of this study was aimed to characterize one of the previously identified putative embryogenic markers known as Eg707 (FJ196136) using a technique called in situ hybridization. The gene expression of Eg707 was detected in all the tested tissues committed to embryogenic pathway as early as in embryogenic callus up to the germinating embryo. Since the formation of proembryo in embryogenic callus is regarded as the first key factor in oil palm somatic embryo development, Eg707 could be used as a potential molecular marker for early detection of oil palm somatic embryogenesis. The third part of this study was aimed to validate the efficiency of previously identified promising candidate embryogenic markers. Expression profile of five oil palm embryogenic-related genes were generated in this study using real time PCR with mRNA from oil palm leaf explant tissues that exhibit different proliferation ability in tissue culture. Two of the transcripts possess a higher potential to be used as a marker as early at the leaf explant stage of the oil palm tissue culture process. The two transcripts were grouped into two categories based on their expression profiles of either continuous or time-dependent. However, the expression profile of each gene did not correlate very well across samples possessing similar proliferation ability from various agencies. Thus, more oil palm genotypes should be analyzed to obtain a more robust selection of the markers for screening of oil palm leaf explants within a particular agency.

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