SANG, TAO*, SONG GE, BAO-RONG LU, AND DE-YUAN HONG. Department of Botany and Plant Pathology, Michigan State University, East Lansing, MI 48824; Laboratory of Systematic and Evolutionary Botany, Institute of Botany, Chinese Academy of Sciences, Beijing 100093; Genetic Resources Center, International Rice Research Institute, 1099 Manila. - Phylogeny of rice genomes.
The rice genus, Oryza (Poaceae), comprises 23 species and nine
recognized genome types. Clarification of phylogenetic relationships
of rice genomes is critical for effective utilization of the wild rice
germplasm. By generating and comparing two nuclear genes (Adh1
and Adh2) trees as well as 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. A new genome type, HHKK, was recognized for O.
schlechteri and Porteresia coarctata, suggesting that P.
coarctata is an Oryza species. Phylogenetic relationship
of the AA genome, which contains cultivated rice, is further
investigated with additional nuclear gene markers.
Key words: allotetraploid, genome, nuclear gene, Oryza, poaceae, rice