Oil Palm - Genomics of Cultivated Palms - page 31

and normal inflorescence of oil palm [37] . While analyzing the 14,537 expressed
sequences of (GenBank accession numbers EL680967-EL695503) from different
tissues of oil palm [38] , a few genes involved in different aspects of flower devel-
opment were also identified. The majority of the genes related to flowering, EgSB,
EgSEP CONSTANS - like , AGAMOUS-like (AGL)2, AGL20, LFY-like, SQUAMOSA,
SQUAMOSA-binding protein (SBP) , and so on, are unique in oil palm and are use-
ful in studying mantled disorder [38] . Flower and etiolated seedling tissue-specific
myo-inositol phosphate synthase-like genes were found in oil palm while studying
the differential gene expression [39] .
cDNA libraries generated from the tissues of male and female inflorescences,
shoot apices, and zygotic embryos (BM402088, BM402089, CN599371-CN601781)
were analyzed to understand mantled disorder [40] . Glycine-rich RNA-binding pro-
teins were seen as a common and abundant gene in all five tissues. A BURP domain-
containing protein and a PVR3-like protein were specific to apical tissues. Storage
proteins (7S globulins and oleosins) were specific to zygotic embryos [40] . A com-
parative study on transcripts of somatic and zygotic embryos revealed the accumu-
lation of globulin 7S during mid to late zygotic embryogenesis, but the absence of
protease activity and transcripts of cysteine proteinase ( CPR ) gene. Transcripts of
three cysteine proteinase genes of the papain family were detected as early as the
second day of in vitro germination [41] . An Eg 707 gene of abscisic acid (ABA) bio-
synthesis was found to display a high degree of expression only in somatic embryo-
genesis in in vitro tissues of oil palm [42] . A recent review of 15 years of research on
mantled disorder provides further details [43] .
3.4 Molecular Markers for QTL Mapping and
Diversity Analysis in Oil Palm
Linkage analysis and QTL mapping experiments in oil palm used a wide range of
molecular markers (AFLP [16,44,45] , cDNA RFLP [46] , SSR [47,48] , and RFLP
[50] ) or a combination of AFLP, AFLP, and SSR [49] . The following is the list of
traits mapped on oil palm genome so far ( Table 3.1 ).
1. Yield and its components (fruit weight and ratio of shell and kernel to fruit [50] ), oil-to-wet
mesocarp ratio [46], and shell thickness [14-19] .
2. Quality (fatty acid composition and iodine value) of oil [49] .
3. Fruit color [45] : Virescence (vir) is a term that describes the change of fruit color in which
mature fruits are emerald green and turn bright orange on ripening. It is a single dominant
gene over Nig [11] .
4. Phenotypic traits of stem and leaf [47,48] .
Molecular markers were also employed to understand the diversity of oil palm
germplasm native to different African and American countries ( Table 3.2 ). AFLP
[51,52] , RAPD [53-57] , RFLP [58-60] , SSR [61-66] , isozymes [67] , and SNP
[68-69] have potential to understand the diversity and also serve as markers to aid
in breeding oil palm. Among the RAPD primers, OPT06 [55] and UBC731 [56]