Introduction - Genomics of Cultivated Palms - page 4

Table 1.3 Botanical Name, Chromosome Number, Genome Size of Important Palms
Compared to Completely Sequenced Genomes of Model Species

Crop Botanical Name Chromosomes Genome Size

(Million base
pairs - Mbp)

Sequenced so
Far (Mbp)

Coconut Cocos nucifera L. 2 n  32 2950 0.07

Oil palm Elaeis guineensis Jacq. 2 n  32 1950 10

Date palm Phoenix dactylifera L. 2 n  36 540 360

Thale cress Arabidopsis thaliana L. 2 n  10 150 150

Rice Oryza sativa L. 2 n  24 400 400

Poplar Populus trichocarpa L. 2 n  38 480 480

using colchicines and oryzalin [18] . Status on genome sequencing and the chromosome
number of important palms vis-à-vis model plants are given in Table 1.3 .

1.3 Molecular Phylogeny and Evolution

Palms are a monophyletic group of plants within the commelinid clade of monocotyle-
dons [19] . Nearly 50 reports of phylogenetic studies of the arecaceae family as a whole
or subfamilies have been published during the past two decades. DNA regions of par-
tial sequences of gene or noncoding regions of four plastid [20] , [maturaseK (matK),
tRNA genes (trnL-trnF), ribosomal protein (rps16 intron), ribulose bisphosphate
carboxylase large subunit (rbcL)], and two low-copy nuclear regions [21] phosphori-
bulokinase (PRK) and RBP2 (intron 2 of RNA polymerase) are used in the studies.
Cloning and sequencing of these six regions was completed in more than 100 species
of palms, and the sequences are available in the public domain. These sequences are
mainly used to find the phylogenetic relationship and infer the evolution of palms.
Recently, other nuclear DNA regions of sequences of WRKY genes [22] and con-
served intron scanning primers [23] have also been are used in palms for the purpose.

1.4 Marker-Trait Associations

Now, many molecular and biochemical markers are available to analyze palm
genomes. Linkage mapping programs have only been undertaken in oil palm and
coconut, to locate the chromosomal regions of agronomic traits and molecular
markers. Specific molecular markers associated with important economic traits are
identified in different palms. Diseases and pests attack the plants and cause serious
economic damage. Molecular markers associated with pest [24] resistance (coconut
eriophyid mite, Figure 1.2 ) and disease [25] resistance (date palm Bayoud disease)
are available and are useful in identifying promising seedlings for planting in pest- or
disease-prone areas. Markers tightly linked to other yield traits are also identified in
palms, such as those for shell thickness in oil palm [26] . Some of the palm species
are dioecious, such as palmyra, date palm, and Calamus (rattan). Identification of sex