Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: July 21, 2005
Publication Date: November 19, 2005
Citation: Gu, X., Kianian, S., Foley, M.E. 2005. Genetics of seed dormancy in weedy rice [abstract]. 5th International Rice Genetics Symposium. p. 124.
Interpretive Summary: Although seed dormancy is a key characteristic of weedy plants, mechanisms 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. In addition, we discovered that most of these genes interact with one another to control the expression of seed dormancy and with genes for other weedy traits to facilitate adaptation. This research will assist in selecting genes to impart resistance to preharvest sprouting and begin to reveal evolutionary mechanisms for adaptation of weeds.
We have developed weedy rice as an experimental system to investigate genetic and evolutionary mechanisms underlying seed dormancy, a key adaptive or domestication-related trait. Dormancy is very strong for most weedy accessions, strong for some traditional cultivars, and weak for modern cultivars, indicating domestication and breeding activities have resulted in a substantial reduction of dormancy. Dormancy in the dormant genotypes is mainly coat-imposed and is associated with other adaptive traits such as shattering, awn, and black hull and red pericarp colors in weedy rice. Heritability for dormancy was much greater in weedy accession- than traditional cultivar-derived crosses. Seven dormancy QTLs have been identified from a wild-like weedy accession, and five of them tightly linked with one to three QTLs for other adaptive traits. Five generations of phenotypic selection alone for dormant extremes introduced five QTL dormancy alleles from the weedy accession to the background of a non-dormant breeding line; four of the five dormancy alleles could not be separated from genes for the other adaptive traits. All seven QTLs interacted with each other through two or higher orders of epistases. The tight linkage and epistases suggest that dormancy has played a central role in co-evolution of an adaptive syndrome and that the dormancy reduction in cultivars largely arose from selections against the related wild or weedy traits. Linkage of adaptive traits also challenges the use of some dormancy genes in breeding varieties resistant to preharvest sprouting. However, the major locus qSD12 does not link with undesirable traits, and thus it may be an ideal candidate gene to impart resistance to preharvest sprouting.