Genetic diversity of Myanmar cultivated rice accessions was evaluated
by DNA markers. The materials included 110 accessions from 6 different
regions of Myanmar and 17 accessions previously analyzed (Doi et al.
2000). Twelve probe-enzyme combinations of restriction fragment length
polymorphism (RFLP) markers (Saito et al. 1991) and 34 PCRbased
polymorphic markers including 5 sequenced tagged site (STS) and 29 cleaved
amplified polymorphic sequence (CAPS) markers (Rice Genome Research Program)
The character was scored as 1 and 0 for the presence and absence of the
fragment, respectively. The 1/0 matrix was used to calculate dissimilarity
coefficients following Nei (1987). The resulting distance matrix was used
to construct an unweighted pair-group method with arithmetic means (UPGMA)
(Sokal and Michener 1958) phenogram using software package PHYLIP (Felsenstein
1993) to infer phylogenetic relationships. The stability of the nodes
in the tree was tested by bootstrap analysis using the same software package.
All accessions except CR351 and CR378 could be distinguished from each
other by at least one DNA marker. The dendrogram revealed 2 well distinguished
groups, named groups I and II (Fig. 1). Group I seemed to correspond Japonica
because it contained the accessions from Japan. It was further divided
into the subgroups Ia and Ib. Most accessions in subgroup Ia are Japonica
varieties originated in Japan, and all accessions contained in subgroup
Ib are Myanmar cultivated rice accessions. Although Myanmar rice accessions
were divided from other Japonica varieties, the genetic distance between
the two subgroups was close and the group I is clearly differentiated
from group II. Typical Indica accessions are contained in group II. It
comprised smaller clusters (IIa, IIb and IIc) plus thirty five accessions
formed no cluster (IId in Fig. 1). Some accessions within group II (designated
as IIe in Fig. 1) are found to be somehow distant from clusters IIa, IIb,
IIc and IId.
Bootstrap analysis was performed to determine the confidence levels of
forks in the phenogram. In the resulting consensus tree only 6 forks had
bootstrap values above 80% (Fig. 2). The grouping of the UPGMA tree and
majority-rule consensus tree were in general comparable except subgroups
IIa, IIb, IIc and IId. The composition of group I (subgroups Ia and Ib)
and subgroup IIe were identical in the both phenograms. However, most
of the forks in subgroups IIa, IIb, IIc and IId showed very low bootstrap
values. The values of bootstrap analysis suggest that constituents of
groups IIa, IIb, IIc and IId may not be significantly differentiated.
The information generated from this experiment would allow geneticists
and breeders to select appropriate materials.
Doi, K., M. Nakano Nonomura, A.Yoshimura, N. Iwata and D.A. Vaughan, 2000.
RFLP relationships of A- genome species in the genus Oryza. J.
Fac. Agr., Kyushu Univ. 45(1): 83-98.
Felsenstein, J., 1993. PHYLIP (Phylogeny Inference Package) version 3.5c.
Distributed by the author. Department of Genetics, University of Washington,
Nei, M., 1987. Molecular Evolutionary Genetics. Columbia University Press,
New York, USA.
Rice Genome Research Program. 332 PCR based genetic markers on rice chromosomes.
Saito, A., M. Yano, N. Kishimoto, M. Nakagahra, A. Yoshimura, K. Saito,
S. Kuhara, Y. Ukai, M. Kawase, T. Nagamine, S. Yoshimura, O. Ideta, R.
Ohsawa, Y. Hayano, N. Iwata and M. Sugiura, 1991. Linkage map of restriction
fragment length polymorphism loci in rice. Jpn. J. Breed. 41: 665-670.
Sokal, K. K., C. D. Michener, 1958. A statistic method for evaluating
systematic relationships. Univ. Kans. Bull. 38: 1409-1438.