DETECTION OF QTL CONTROLLING DORMANCY RELATED TRAITS IN Populus

¹ University of Washington, 3501 NE 41st St., Seattle, WA 98195 USA

² Oregon State University, Corvallis, OR 97331-7304 USA

³ Ohio State University, School of Natural Resources, Wooster, OH 44691 USA

⁴ University OF Gent, K. L. Ledeganckstraat 35, B-9000, Gent, Belgium

The annual period of dormancy that temperate woody perennials experience is crucial for surviving the cold temperatures of winter. Variation in the timing of the onset and release from this dormant period occurs in poplars over the wide latitudinal range they occupy. We investigated the genetic basis of this variation in an F2 hybrid pedigree of Populus. Five QTL for bud flush (release from dormancy) and two QTL for bud set (onset of dormancy) were identified. We mapped five candidate genes which might plausibly be involved in the control of dormancy: abi1b, abi1d, abi3, phyb1, phyb2. The genes abi1d, abi3, and phyb1 mapped to linkage groups on which we found no QTL. phyb2 mapped to the same marker interval as a bud flush QTL. The adjacent marker interval contains a bud set QTL. abi1b mapped to the same marker interval as a different flush QTL. A test of analysis of variance comparing the mean days to bud flush of the three genetic classes (paternal and maternal homozygotes and heterozygotes) was significant for both abi1b and phyb2. These findings were compared to mapping of bud flush QTL previously done in a different hybrid poplar pedigree (Family 331). A bud flush QTL was detected on the linkage group to which abi1b mapped in Family 331 and an analysis of variance showed significant differences in means among the abi1b genetic classes. An other flush QTL occurs on a linkage group homologous to a linkage group in Family 331 which also contains a flush QTL.