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United States Department of Agriculture

Agricultural Research Service

Research Project: RESPONSE OF DIVERSE RICE GERMPLASM TO BIOTIC AND ABIOTIC STRESSES

Location: Dale Bumpers National Rice Research Center

Title: The short and the long of it: SD1 polymorphism and the evolution of growth trait divergence in U.S. weedy rice

Authors
item Reagon, Michael -
item Thurber, Carrie -
item Olsen, Kenneth -
item JIA, YULIN
item Caicedo, Ana -

Submitted to: Molecular Ecology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: July 3, 2011
Publication Date: September 12, 2011
Citation: Reagon, M., Thurber, C.S., Olsen, K.M., Jia, Y., Caicedo, A.L. 2011. The short and the long of it: SD1 polymorphism and the evolution of growth trait divergence in U.S. weedy rice. Molecular Ecology. 20:3743-3756.

Interpretive Summary: Rapid growth is thought to be an adaptive weedy trait. U.S. weedy rice, a major conspecific weed of cultivated rice (Oryza sativa), displays variation for growth traits. In the current study, we reported five growth traits in samples of weedy, cultivated, and wild rice. Patterns of polymorphism in the growth candidate gene, SD1 were determined and compared to flanking genomic regions and a previously described reference set of 48 gene fragments. Considerable variation for growth traits was found among weed groups. We also found that a large chromosomal block containing the SD1 allele was introgressed from tropical japonica, the predominant rice cultivar in the U.S., in one weedy rice population, and is associated with a change in growth patterns. These findings suggest that phenotypic divergence from cultivated ancestors has occurred in weedy rice, and that growth trait convergence is not evident among weedy rice populations. These data further support a hypothesis that introgressive hybridization is one of the means to promote evolutionary diversity in weedy rice.

Technical Abstract: Growth related traits are thought to enhance competitiveness of agricultural weeds. U.S. weedy rice, a major conspecific weed of cultivated rice (Oryza sativa), displays variation for growth traits. Prior studies have shown that major U.S. weedy rice populations likely evolved from domesticated groups that are not locally cultivated. We attempt to determine whether growth trait divergence has occurred among U.S. weed groups and their putative progenitors. We further evaluate mechanisms that may have led to evolution of divergent phenotypes. Our study assesses five growth traits in a common garden in samples of weedy, cultivated, and wild rice. We also determine patterns of polymorphism in SD1, and compare these to flanking genomic regions and a previously described reference set of 48 gene fragments. We find considerable variation for growth traits among weed groups, and observe shifts in trait distribution between weeds and their ancestral populations. Introgression of a large chromosomal block containing the SD1 allele from tropical japonica, the predominant rice cultivar in the U.S., has occurred in one weedy rice population, and is associated with a change in growth patterns. Our results show that phenotypic divergence from cultivated ancestors has occurred in weedy rice evolution, and that growth trait convergence is not evident among weedy rice populations. Our study is one of the first examples supporting introgressive hybridization as promoting evolutionary divergence in weedy rice.

Last Modified: 9/10/2014
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