Submitted to: Genetica
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/24/2004
Publication Date: 10/1/2004
Citation: Gu, X.-Y., Foley, M.E., Chen, Z.-X. 2004. A set of three genes regulates photoperiodic responses of flowering in rice (Oryza sativa). Genetica. 122:127-140. Interpretive Summary: Flowering time and photoperiod sensitivity are an important agronomic characteristics governing the production of crops. There is limited information on the genetic controls of flowering time and photoperiod in rice. Separately, and in conjunction with our research on seed dormancy in rice, we evaluated flowering time and photoperiod response in several crosses using rice varieties that have a mid-range response. We discovered that three genes control flowering time and photoperiod in these crosses. This research will set the stage for further characterization of genes that regulate these traits, and allow us to select a rapid flowering and photoperiod insensitive line for developing populations useful for research on seed dormancy.
Technical Abstract: Crosses where the F1s flower later than the late-flowering parents were chosen to identify major genes for flowering time from naturally occurring variants in rice, a short-day plant. Initial experiments were conducted under the natural day length using four mid-season varieties as parents. Genetic analysis categorized the parental lines into two groups with respect to three major genes. These genes controlled the F1-delayed flowering and the F2 bimodal distribution by three-locus complementation, and regulated flowering time at the different levels by additional intra- and inter-locus interactions. A triple mutant with an extremely early flowering time was selected based on the above model. Subsequent experiments conducted under different day lengths indicated that this set of genes controls photoperiod sensitivity (PS) and the trihybrid has a critical photoperiod between 13.5 and 14 h. We propose that development of a set of complementary testers will facilitate discovery of major PS genes or alleles from naturally occurring variants, and conclude that the critical photoperiod is a synergistic effect among a set of PS genes in rice.