Submitted to: Theoretical and Applied Genetics
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: January 24, 2005
Publication Date: March 22, 2005
Citation: Gu, X.-Y., Kianian, S.F., Hareland, G.A., Hoffer, B.L., Foley, M.E. 2005. Genetic analysis of adaptive syndromes interrelated with seed dormancy in weedy rice (Oryza sativa). Theoretical and Applied Genetics. 110:1108-1118.
Interpretive Summary: Seed dormancy in weeds and resistance to cereal grain crops are important issues in crop production. 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. The interrelationship among these characteristics suggests they are an adaptation for the persistence and survival of weedy strains.
Seed dormancy in rice interrelates to the weedy characteristics shattering, awn, black hull color and red pericarp color. A cross between the weedy strain SS18-2 and the breeding line EM93-1 was developed to investigate the genetic basis and adaptive significance of the interrelationships. These characteristics differed in dominance from complete to incomplete, in heritability from 0.5 to 0.96, and in their contribution to phenotypic or genotypic variation in dormancy up to 25%. Five dormancy, 4 shattering, and 3 awn-length QTLs were detected in the BC1 population replicated in two years. Two QTLs for hull color were identified, and the SS18-2- and EM93-1-derived alleles increased the intensity of black, and red or yellow pigmentations, respectively. The only QTL for pericarp color co-located with the red pericarp gene Rc, with the SS18-2-derived allele increasing the intensity of black and red pigmentations. Four of the 5 dormancy QTLs were flanked or bracketed by 1 to 4 QTLs for the interrelated characteristics. The QTL organization pattern indicates the central role of seed dormancy in adaptive syndromes for non-domesticated plants, implies elimination of dormancy from cultivars could arise from the selections against multiple interrelated characteristics, and challenges the use of dormancy genes at these loci in breeding varieties for resistance to pre-harvest sprouting (PHS). However, another QTL (qSD12) provides candidate gene(s) for PHS resistance because it has a large effect in the population and it is independent of the loci for interrelated characteristics.