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Phylogeny of Rice Genomes with Emphasis on Origins of Allotetraploid Species
Song Ge, Tao Sang, Bao-Rong Lu and De-Yuan Hong
Proceedings of the National Academy of Sciences of the United States of America
Vol. 96, No. 25 (Dec. 7, 1999), pp. 14400-14405
Published by: National Academy of Sciences
Stable URL: http://www.jstor.org/stable/121416
Page Count: 6
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The rice genus, Oryza, which comprises 23 species and 9 recognized genome types, represents an enormous gene pool for genetic improvement of rice cultivars. Clarification of phylogenetic relationships of rice genomes is critical for effective utilization of the wild rice germ plasm. By generating and comparing two nuclear gene (Adh1 and Adh2) trees and a chloroplast gene (matK) tree of all rice species, phylogenetic relationships among the rice genomes were inferred. Origins of the allotetraploid species, which constitute more than one-third of rice species diversity, were reconstructed based on the Adh gene phylogenies. Genome types of the maternal parents of allotetraploid species were determined based on the matK gene tree. The phylogenetic reconstruction largely supports the previous recognition of rice genomes. It further revealed that the EE genome species is most closely related to the DD genome progenitor that gave rise to the CCDD genome. Three species of the CCDD genome may have originated through a single hybridization event, and their maternal parent had the CC genome. The BBCC genome species had different origins, and their maternal parents had either a BB or CC genome. An additional genome type, HHKK, was recognized for Oryza schlechteri and Porteresia coarctata, suggesting that P. coarctata is an Oryza species. The AA genome lineage, which contains cultivated rice, is a recently diverged and rapidly radiated lineage within the rice genus.
Proceedings of the National Academy of Sciences of the United States of America © 1999 National Academy of Sciences