Submitted to: Meeting Abstract
Publication Type: Abstract only
Publication Acceptance Date: 10/5/2004
Publication Date: 1/15/2005
Citation: Gu, X., Kianian, S., Foley, M.E. 2005. Introduction of seed dormancy genes from weedy to cultivated rice (Oryza sativa) by phenotypic selection. [Abstract] Plant & Animal Genome XIII Conference. P.144. Interpretive Summary: Seed dormancy is an important adaptive trait for the persistence of weeds. We are using weedy rice as a model system to investigate seed dormancy and pre-harvest sprouting. We screened a number of weedy strains and domesticated cultivars of rice for the type and depth of dormancy. Then, selected weedy strains were crossed and backcrossed to a non-dormant rice breeding line for genetic analysis of the relationship between dormancy and the seed shattering, awn, hull color, and pericarp/testa color characteristics. We discovered that all these characteristics are interrelated and the weedy form of the trait tends to reduce germination, that is, increase covering-imposed seed dormancy. However, the dormancy gene on chromosome 12 seems to be independent of genes for other weed characteristics, and may therefore have potential to impart resistance to preharvest sprouting.
Technical Abstract: Seed dormancy in weedy rice is associated with awn and pigmentations on the hull and pericarp. Phenotypic selection for germinability and the morphological characteristics was employed to introduce dormancy genes from the weedy strain SS18-2 to the genetic background of the breeding line EM93-1. Selection started with an F2 and continued in the following five generations of cross or backcross (BC) F1 populations. The SS18-2-derived genomic regions in the selected F2 to BC3F1 individuals include the previously identified dormancy quantitative trait loci (QTL) qSD4, 7-1, 8, and 12 as determined by 150 markers distributed over the 12 chromosomes. Two dormant BC4F1 plants (#044 and #132) were selected to generate the F2 populations. The plant #044 is heterozygous for the regions containing qSD4, 7-1 and 8; these QTL closely link with the loci for one or two of the three characteristics in the BC4F2 population. The plant #132 is heterozygous for the regions containing qSD7-1 and 12; qSD7-1 also could not be separated from the red pericarp gene Rc, and qSD12 accounted for about 60% of the phenotypic variance in the BC4F2 population. These results indicates that the phenotypic selections can be used to transfer dormancy genes from non-domesticated to cultivated rice, but the linkage drag may challenge the use of some dormancy genes in breeding varieties resistant to pre-harvest sprouting (PHS). In contrast, the dormancy allele at SDS-12 should be the best candidate because of its major effect and independence from some undesirable weedy characters.