| Summary: | 碩士 === 國立中興大學 === 植物學系 === 83 === Pedigree analysis was performed for 11 Japonica rice
(Oryza sativa L.)cultivars released between 1988-1994 and 19
Indicarice cultivars released between 1957-1988.Examination
of pedigrees indicated that modern Taiwan Japonicae could be
traced back to 68 ancestors.Two ancestors,''Shinriki'' and
''Kameji'',had the highest mean relative genetic contributions of
the genes with 16 % and 12 %, respectively. The 10 most
important ancestral contributors of the 11 Japonica rice
collectively comprised 58% of genetic contribution.
Germplasm of diverse sources and Indica type were
incorperated to increase the genetic diversity.Modern
Japonica rice varieties were developed with a broad
genetic base. 19 Indica rice cultivars could be traced
back to 44 ancestors. DGWG appeared most frequently in
19 Indica parentages and contributed 23% of the genetic
constitution of the cultivars. Ten ancestors together
comprised 77% in mean relative contribution. This result
revealed the narrow genetic base in Indica rice cultivars.
Cluster analysis produced two large groups of Japonica and
Indica cultivars. Four small groups A'',B'', C'' and D'' of
Japonica rice can be traced back to four predominant
parents ''Taichung 65'', ''Kaohsiung 141'', ''Tainan 5''and
''Chianung line 702361'', respectively. Kaohsiung sel. 1,
Taiken 1, Taiken 7 and Taiken 9 did not belong to any of these
four groups. Three small groups E'', F'' and G'' of Indica rice
can be traced back to three predominant parents of ''DGWG'',
''IR8'' and ''IR22''. The cluster analysis revealed that
Indica rice cultivar are not broadly based, but
reasonable genetic diversity occurs among these genotypes.
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