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United States Department of Agriculture

Agricultural Research Service

Research Project: RESPONSE OF DIVERSE RICE GERMPLASM TO BIOTIC AND ABIOTIC STRESSES Title: Molecular evolution of the sh4 shattering locus in U.S. weedy rice

Authors
item Thurber, Carrie -
item Reagon, Michael -
item Gross, Briana -
item Olsen, Kenneth -
item Jia, Yulin
item Caicedo, Ana -

Submitted to: Molecular Ecology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: February 19, 2010
Publication Date: June 24, 2010
Citation: Thurber, C.S., Reagon, M., Gross, B.L., Olsen, K.M., Jia, Y., Caicedo, A.L. 2010. Molecular evolution of the sh4 shattering locus in U.S. weedy rice. Molecular Ecology. 19:3271-3284.

Interpretive Summary: Shattering is one of the predominant weedy traits of rice. In the United States, it was known that the genomic identity of weedy rice is shared with exotic domesticated cultivars. The shattering phenotype in a collection U.S. weedy rice accessions, as well as wild and cultivated relatives previously characterized for genomic diversity was investigated. In contrast to a decrease in shattering ability seen in cultivated groups it was found that all U.S. weedy rice groups shatter seeds easily regardless of origin. We sequenced the shattering locus, sh4, in weedy rice; showing that all cultivated and weedy rice share similar haplotypes at sh4, and all contain a single derived mutation associated with decreased seed shattering. Our data suggest strongly that weed rice was evolved from domesticated backgrounds.

Technical Abstract: Cultivated rice fields worldwide are plagued with weedy rice, a congeneric weed of cultivated rice (Oryza sativa L.). The persistence of weedy rice has been attributed, in part, to its ability to shatter (disperse) seed prior to crop harvesting. In the United States, separately evolved weedy rice groups have been shown to share genomic identity with exotic domesticated cultivars. Here, we investigate the shattering phenotype in a collection U.S. weedy rice accessions, as well as wild and cultivated relatives previously characterized for genomic diversity. We find that all U.S. weedy rice groups shatter seeds easily, despite multiple origins, and in contrast to a decrease in shattering ability seen in cultivated groups. We assessed allelic identity and diversity at the major shattering locus, sh4, in weedy rice; we find that all cultivated and weedy rice, regardless of population, share similar haplotypes at sh4, and all contain a single derived mutation associated with decreased seed shattering. Our data constitutes the strongest evidence to date of an evolution of weeds from domesticated backgrounds. The combination of a shared cultivar sh4 allele and a highly shattering phenotype, suggests that U.S. weedy rice groups must have re-acquired the shattering trait after divergence from their progenitors through alternative genetic mechanisms.

Last Modified: 12/18/2014
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