| Institution: | (1) Molecular Tree Breeding Services, LLC, 21040 Flumerfelt Rd. SE, Centralia, WA 98531, USA;(2) Institute of Forest Genetics, Pacific Southwest Research Station, USDA Forest Service, Davis, CA 95616, USA;(3) Department of Forest Sciences, Faculty of Forestry, University of British Columbia, 2424 Main Mall, Vancouver, BC, Canada, V6T 1Z4;(4) Department of Forest Science, Oregon State University, Corvallis, OR 97331-5752, USA;(5) Department of Environmental Horticulture, University of California, Davis, CA 95616, USA |
| Abstract: | Quantitative trait locus (QTL) analyses are used by geneticists to characterize the genetic architecture of quantitative traits, provide a foundation for marker-aided-selection (MAS), and provide a framework for positional selection of candidate genes. The most useful QTL for breeding applications are those that have been verified in time, space, and/or genetic background. In this study, spring cold-hardiness of Douglas-fir foliar tissues was evaluated in two clonally replicated (n=170 and 383 clones) full-sib cohorts derived from the same parental cross in two different years (made 5 years apart). The cohorts were established in widely separated forest test sites and tissues were artificially freeze tested using different cold injury assessment methods. Four of six unique QTL detected for spring cold-hardiness in needles of Cohort 1 were tentatively verified in the second cohort. Four additional QTL were detected in Cohort 2, two on linkage groups (LGs) not previously represented in the smaller cohort. In total, 10 unique QTL were identified across both cohorts. Seventeen of twenty-nine putative cold-hardiness candidate genes (Douglas-fir ESTs) placed on the Douglas-fir linkage map locate within the 95% confidence intervals of spring needle cold-hardiness QTL from the two cohorts and thus represent priority targets for initiating association mapping in Douglas-fir. |
