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United States Department of Agriculture

Agricultural Research Service

Title: The evolutionary genomics of weedy red rice in the U.S.A.

Authors
item Olsen, Kenneth - WASHINGTON UNIV.
item Caicedo, Ana - UNIV. OF MASS
item Jia, Yulin

Submitted to: Journal of Integrative Plant Biology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: January 2, 2007
Publication Date: March 15, 2007
Citation: Olsen, K.M., Caicedo, A.L., Jia, Y. 2007. The evolutionary genomics of weedy red rice in the U.S.A. Journal of Integrative Plant Biology. 49:811-816.

Interpretive Summary: Red rice is an interfertile, weedy form of cultivated rice (Oryza sativa) that competes aggressively with the crop in the southern U.S., reducing yields and contaminating harvests. Understanding of origin, evolution, and domestication of red rice would help the development of strategies to control red rice. No wild Oryza species occur in North America, and the weed has been proposed to have evolved through multiple mechanisms, including 'de-domestication' of U.S. crop cultivars, accidental introduction of Asian weeds, and hybridization between U.S. crops and Asian wild/weedy Oryza strains. The phenotype of U.S. red rice ranges from 'crop mimics,' which share some domestication traits with the crop, to strains closely resembling Asian wild Oryza species. Assessments of genetic diversity have indicated that many weed strains are closely related to Asian taxa (including indica and aus rice varieties, which have never been cultivated in the U.S., and the Asian crop progenitor, O. rufipogon), while others show genetic similarity to the tropical japonica varieties cultivated in the southern U.S. Our ongoing research on the genomic diversity of this weed at seven well defined loci will provide a fine-scale assessment of how these population genetic forces have interacted to generate the weed-adaptive phenotypes that have enabled this pest species to compete so aggressively in U.S. agricultural fields. The absence of native Oryza species in North America and the narrow germplasm pool of U.S. rice varieties makes U.S. red rice a particularly tractable system for examining these processes. The findings from this work may will offer a useful starting point for examining weedy rice evolution in the genetically more complex systems found in Asia.

Technical Abstract: Red rice is an interfertile, weedy form of cultivated rice (Oryza sativa) that competes aggressively with the crop in the southern U.S., reducing yields and contaminating harvests. No wild Oryza species occur in North America, and the weed has been proposed to have evolved through multiple mechanisms, including 'de-domestication' of U.S. crop cultivars, accidental introduction of Asian weeds, and hybridization between U.S. crops and Asian wild/weedy Oryza strains. The phenotype of U.S. red rice ranges from 'crop mimics,' which share some domestication traits with the crop, to strains closely resembling Asian wild Oryza species. Assessments of genetic diversity have indicated that many weed strains are closely related to Asian taxa (including indica and aus rice varieties, which have never been cultivated in the U.S., and the Asian crop progenitor, O. rufipogon), while others show genetic similarity to the tropical japonica varieties cultivated in the southern U.S. Here we review what is known about the evolutionary origins and genetic diversity of U.S. red rice, and we describe an ongoing research project to further characterize the evolutionary genomics of this aggressive weed.

Last Modified: 4/21/2014
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