Submitted to: Heredity
Publication Type: Peer reviewed journal
Publication Acceptance Date: 8/15/2005
Publication Date: 1/1/2006
Citation: Gu, X., Kianian, S., Foley, M.E. 2006. Isolation of three dormancy QTLs as Mendelian factors in rice. Heredity. 96(1):93-99. Interpretive Summary: Seed dormancy is a key characteristic of weedy plants. In the course of our research to develop weedy rice as a system to map-base clone dormancy quantitative trait loci (QTL), we used marker assisted selection and backcrossing techniques to isolate the QTLs qSD1, qSD7-1, and qSD12 into individual populations to confirm the QTLs and estimate genetic parameters for individual QTLs in synchronized genetic backgrounds.
Technical Abstract: Seed dormancy is a key adaptive trait under polygenic control in many plants. We introduced dormancy genes from the weedy rice accession SS18-2 into the non-dormant genetic background of EM93-1 rice to examine component genes and afterripening effects of individual QTLs on dormancy and germination. A BC4F2 plant, which was heterozygous for SS18-2-derived qSD1, 7-1, and 12 chromosomal regions, was selected to develop the BC4F3 population. Single point analysis detected effects of qSD7-1 and qSD12 (R2 = 38 to 72%) on germination of seeds afterripening under warm, dry conditions for 10, 30, and 50 days (DAR) in the population. However, multiple linear regression analysis detected genotypic effects of the three QTLs and trigenic epistasis; a main effect of time of afterripening (Environment); and interactions of E with qSD12 and with the qSD1'qSD7-1 and qSD7-1'qSD12 epistases. The linear model demonstrates that genotypic effects on germination varied with DAR, and that some epistasis or epistasis-by-E interactions partially counteract QTL main effects. The three QTLs were isolated as single Mendelian factors from the BC4F3 population and estimated for component gene effects in BC4F4 populations. Isolation improved estimation of the qSD1 effect and confirmed the major effect of qSD12. The qSD1 and qSD12 loci displayed a gene additive effect. The qSD7-1, which was further narrowed to a chromosomal region encompassing the red pericarp color gene Rc, displayed gene additive and dominant effects.