Biology Reference
In-Depth Information
3.7 Haploid Technologies
Inbred lines can capture and enhance the efficiency of heterosis breeding.
Development of inbred lines in a perennial crop takes many years and requires
experimental space. The use of haploids and doubled haploids as parents for F1 vari-
ety production is a potential area of interest in oil palm. Spontaneous occurrence
of haploids at very, very low frequencies is reported. Flow cytometric analysis in
oil palm provides the quantification of nuclear DNA content. The genome size of
African oil palm is 2C
3.76
0.09 pg, which means a genome size of 3.4
10
9
bp
[84]
. A high-throughput screen involving morphological traits, molecular (microsat-
ellite) markers, and flow cytometry
[84]
is developed
[85]
to identify spontaneously
formed haploid (H) and doubled haploid (DH) palms. Nearly 1000 haploids includ-
ing a single doubled haploid plant were located using the method
[85]
.
3.8 Road Map for Oil Palm Genomics
Genetics, genomics, and transgenic technologies have been exploited to a greater
extent in oil palm than in any other cultivated palm. Studies of transcripts in somatic
embryogenesis, mantled disorder, mescoarp, and other tissues are exhaustive in oil
palm. Molecular markers and genome mapping of shell thickness and mesocarp
traits are an important advancement in oil palm. Identification of markers associ-
ated with other traits such as dwarf habit and disease resistance is a future priority
in oil palm. Such knowledge complements the heterosis of shell thickness exploited
through conventional breeding. Haploid technologies coupled with genome-
wide selection using markers can bring additional yield enhancement in the high-
est oil-bearing palm crop. MAP-based cloning of a genomic fragment nearing the
shell thickness locus at the terminal region of chromosome 4 is an important future
genomics priority. A molecular marker kit or DNA chips for identification of ten-
era seedlings with 100% precision is the next immediate research priority. Whole
genome shotgun sequencing
[86]
is in progress, which can provide knowledge of
the complete genome for oil palm, the next palm species being studied. Research
on transcription factors, genes, and promoters cloned from oil palm gives additional
tools to oil palm improvement as markers or accessories in transgenics. Studies in
retrotransposons
[87]
and DNA methylation
[88]
offer additional knowledge of
markers in the assessment of diversity in oil palm.
Comprehensive genomic information available in oil palm and a complete
genome of date palm offer promise in comparative genomics of other palms. By
employing sequence conservation, researchers can transfer the knowledge to other
cultivated palms. A few molecular markers have already offered promise in other
palm species. In the near future, we anticipate obtaining the complete genome
sequence of oil palm and sequence information of many genes and promoters.
Genes and promoters of defense-related traits offer protection of oil palm from
biotic and abiotic stress factors. Proteomics investigations in important processes of
