Submitted to: Molecular Ecology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 10/21/2012
Publication Date: 1/16/2013
Publication URL: http://handle.nal.usda.gov/10113/57989
Citation: Thurber, C.S., Jia, M.H., Jia, Y., Caicedo, A. 2013. Similar traits, different genes? Examining convergent evolution in related weedy rice populations. Molecular Ecology. 22:685-698. doi: 10.1111/mec.12147. Interpretive Summary: Understanding of evolutionary mechanisms of invasive species of rice can benefit crop improvement and weed management. In the present study, quantitative trait loci (QTL) underlying weedy traits of rice were compared to investigate the possibility if parallel genetic evolution was occurred in two distinct populations of weedy rice in the U.S. F2 offspring from crosses between an indica cultivar, and two ecotypes from genetically differentiated U.S. weedy rice populations were used to map QTL for four quantitative traits, heading date, seed shattering, plant height, and growth rate under controlled environmental conditions. QTL were mapped on six rice chromosomes without overlapped between the two populations. Shared QTL among weed groups were only observed for heading date, a trait for which both weedy groups have diverged from their cultivated ancestors and from each other. We suggest that genes for heading date may be evolved in weedy rice under selection and domestication. However, we have not identified overlapped QTLs of the remaining traits in these two weedy groups suggesting they were evolved to the same environment through different genetic mechanisms.
Technical Abstract: Convergent phenotypic evolution may or may not be associated with parallel genotypic evolution. Agricultural weeds have repeatedly been selected for weed-adaptive traits such as rapid growth, increased seed dispersal and dormancy, thus providing an ideal system for the study of parallel evolution. Here we identify QTL underlying weedy traits and compare their genetic architecture to assess the potential for parallel genetic evolution in two distinct populations of weedy rice. F2 offspring from crosses between an indica cultivar and two individuals from genetically differentiated U.S. weedy rice populations were used to map QTL for four quantitative (heading date, seed shattering, plant height, and growth rate) and two qualitative traits. We identified QTL on six of the twelve rice chromosomes, yet most QTL locations do not overlap between the two populations. Shared QTL among weed groups were only seen for heading date, a trait for which both weedy groups have diverged from their cultivated ancestors and from each other. The sharing of some QTL with wild rice also suggests a possible role in weed evolution for genes under selection during domestication. The lack of overlapping QTL for the remaining quantitative traits suggests that, despite a close evolutionary relationship, weedy rice groups have adapted to the same agricultural environment through different genetic mechanisms.