QTL mapping in interspecific hybrids of forest trees
1994
Bradshaw, H.D. (Washington Univ., Seattle (USA). Center for Urban Horticulture) | Grattapaglia, D.
Interspecific hybridization leads to heterosis for growth in a significant number of forest tree genera. When it is possible to exploit this heterosis by vegetative propagation, as is currently the case in the hardwood genera Eucalyptus and Populus, interspecific hybridization is often the preferred route to genetic gain. The genetic basis of variation among hybrid offspring and the genetic mechanisms underlying heterosis observed in interspecific hybrids in forest trees are poorly understood, however. A deeper understanding of the genetic control of growth in interspecific hybrids will be necessary to design and implement long-term breeding strategies. We have produced linkage maps of F1 and F2 interspecific hybrids in Eucalyptus and Populus, respectively, in order to address these unresolved issues. We have identified quantitative trait loci (QLTs) with major effects on stem growth, form, leaf phenology, wood quality, disease resistance, and organogenesis in vitro. Patterns of QTL inheritance for gross phenotypic traits, e.g., stem volume growth and circumference, have been compared with QLTs identified for physiological and anatomical correlates of these traits, e.g., sylleptic branch leaf area and wood specific gravity. Co-localization of QTLs suggests novel approaches to indirect selection in clonally propagated interspecific hybrids. Significant questions of QTL constancy across families, tree age, and environment remain to be studied
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