Comparative mapping of seed dormancy loci between tropical and temperate ecotypes of weedy rice (Oryza sativa L.)

Authors: ZHANGA, LIHUA - South Dakota State University; LOUA, JIEQIONG - South Dakota State University; GU, XING-YOU - South Dakota State University; Foley, Michael

Submitted to: Genes, Genomes, Genetics
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 6/2/2017
Publication Date: 8/1/2017
Citation: Zhanga, L., Loua, J., Foley, M.E., Gu, X.-Y. 2017. Comparative mapping of quantitative trait loci for seed dormancy between tropical and temperate ecotypes of weedy rice (Oryza sativa L.). Genes, Genomes, Genetics. 7(8):2605-2614. https://doi.org/10.1534/g3.117.040451.
DOI: https://doi.org/10.1534/g3.117.040451

Interpretive Summary: Seed dormancy is an important characteristic for the persistence of weeds. This research used weedy rice as a model system and genetic techniques to investigate differences and similarity of seed dormancy genes between distinct ecotypes of temperate versus tropical origin. Using a technique called quantitative trait locus mapping, we identified a total of 12 loci associated with seed dormancy in populations developed from a temperate-ecotype weedy rice line. Nine of the 12 loci were mapped to the same positions as those previously identified for a tropical-ecotype weedy rice line. The high number of common loci suggests that weed populations represented by the tropical and temperate lines share a core set of seed dormancy genes likely due to phenotypic selections for some inter-related wild-type characters like seed shattering, black hull and red pericarp colors, and long awn, controlled by linked or pleiotropic genes in the model system.

Technical Abstract: Genotypic variation for seed dormancy (SD) in a species contributes to plant adaptation and weed persistence in agroecosystems. This research aimed to address the similarity of SD genes between distinct ecotypes using weedy rice as a model system. Quantitative trait locus mapping identified a total of 12 loci associated with SD in a primary and two advanced backcross populations developed from a line of temperate-ecotype weedy rice. This weed line retained the dormancy-enhancing allele at 10 (83%) of the 12 loci. Nine (75%) of the 12 loci were mapped to the same positions as those previously identified for a line of tropical-ecotype weedy rice. The high similarity suggests that weed populations represented by the tropical and temperate lines share a majority of genes for the adaptive trait, although these two ecotypes differ in latitudinal distribution by about 27° in the northern hemisphere. A core set of SD genes was maintained in the distinct ecotypes partly because of phenotypic selections for some inter-related wild-type characters (e.g., seed shattering, black hull and red pericarp colors, and long awn) controlled by linked or pleiotropic genes in the model system. Both of the weed populations contain the dormancy-reducing allele at a few loci that are also associated with plant height; thus natural selection against reduced plan height helped maintain the SD genotypic diversity. SD genes conserved across ecotypes could be used as targets to develop transgenic mitigation approaches to reduce the risk of gene flow from genetically modified crops into weed/wild relatives.