Submitted to: Workshop Proceedings
Publication Type: Book / Chapter
Publication Acceptance Date: 11/27/2006
Publication Date: 2/1/2007
Citation: Foley, M.E., Gu, X., Kianian, S.F. 2007. Quantitative Trait Loci, Epistasis, and Other Interactions Associated with Dormancy in Weedy Rice (Oryza sativa L). Workshop Proceedings. CAB International 2007. Seeds: Biology, Development and Ecology. 22:217-224. Interpretive Summary: Although seed dormancy is a key characteristic of weedy plants, mechanism governing seed dormancy are unknown. We seek to map and clone dormancy genes from rice to elucidate mechanism governing seed dormancy in weedy grasses . To this end, we developed a backcross population using the weedy strain of rice called SS18-2 and constructed a genetic linkage map. Using seed germination data, the linkage map, and genetic software, we identified several genes that regulate dormancy in this population over a 21 day period of afterripening. Finally, we discovered that these genes interact with one another, with the environment, and with other genes in the population to control the expression of seed dormancy.
Technical Abstract: A wild-like weedy strain SS18-2 was selected to investigate the genetic architecture underlying seed dormancy. A framework genetic map covering the whole rice genome was constructed based on 156 backcross, i.e., BC1 [EM93-1(non-dormant breeding line)//EM93-1/SS18-2] individuals. The mapping population was replicated using a splitting-tiller technique to control and better estimate the environmental variation. Dormancy was determined by germination of seeds after 1, 11, and 21 days of after-ripening (DAR). Six dormancy QTLs, designated as qSDS-4, -6, -7-1, -7-2, -8, and -12, were identified. The locus qSDS-7-1 was tightly linked to the red pericarp color gene Rc. In addition, the locus qSDS-4 was associated with an interval imparting black hull color. A QTL×DAR interaction was detected for qSDS-12, the locus with the largest main effect at 1, 11, and 21 DAR (R2 = 0.14, 0.24, and 0.20, respectively). Two and higher (three and four) orders of epistases were detected with 4 and all of the 6 QTL, respectively. The higher-order epistases strongly suggests the presence of genetically complex networks in the regulation of variation for seed dormancy in natural populations, and makes it critical to select for a favorable combination of alleles at multiple loci in positional cloning of a target dormancy gene. Backcrossing techniques in combination with phenotypic and marker-assisted selection are being used to introduce the weedy rice derived dormancy locus qSDS-7-1 into the EM93-1 genetic background to develop near isogenic lines for fine mapping and positional cloning.