Submitted to: Crop Science
Publication Type: Peer reviewed journal
Publication Acceptance Date: 8/1/2005
Publication Date: 5/1/2005
Citation: Gu, X-Y., Kianian, S.F., Foley, M.E. 2005. Seed dormancy imposed by covering tissues interrelates to shattering and seed morphological characteristics in weedy rice. Crop Science. 45:948-955. Interpretive Summary: Seed dormancy in weeds and resistance to in 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.
Technical Abstract: Seed dormancy is a major adaptive trait in plants and provides resistance to pre-harvest sprouting in cereal crops and facilitates the survival of weeds. Seventeen weedy strains of rice (Oryza sativa L.) and 24 domesticated varieties were evaluated for germinability to screen for donors of dormancy genes. Extremely dormant genotypes were identified from the weedy strains. These genotypes displayed hull- and pericarp/testa-imposed dormancy. Three dormant weedy strains LD, TKN12-2, and SS18-2 were crossed and backcrossed with the breeding line EM93-1 to determine the relationship between dormancy and the shattering, awn, hull color, and pericarp/testa color characteristics. All these characteristics interrelated to the covering-imposed dormancy; the weedy forms of the characteristics significantly reduced germination in the BC1F1 populations. Moreover, multiple linear regression analyses revealed significant interaction effects between the characteristics on dormancy in the populations. The interrelation and interaction reflect the importance of combined effects of dormancy and other weedy characteristics in the adaptation of weedy populations to agroecosystems, and suggests that domestication and breeding activities have eliminated dormancy alleles at loci near the genes for shattering and the morphological characteristics from improved varieties.