Quantitative trait loci affecting stomatal density and growth in a Quercus robur progeny: implications for the adaptation to changing environments

Stomatal traits are important to cope with changes in levels of atmospheric carbon dioxide (CO 2 ) and with changing availability of water. Thus, they are expected to be involved in the reactions of plants to climate change. They are known to show a plastic physiological response to environmental factors such as elevated CO 2 concentrations, but they are also under genetic control and should undergo evolutionary change if selection differs among environments. Stomatal development is regulated by several environmental and genetic signals suggesting a polygenic inheritance. In the present study, F 1 progeny derived from a cross between Quercus robur and Q. robur subsp. slavonica were used to map QTLs (quantitative trait loci) for stomatal densities and growth parameters under nonwater stress conditions in 2 and 3 consecutive years, respectively. The positions of QTLs for stomatal density and growth coincided on six linkage groups. The QTL allele associated with the higher stomatal density was generally associated with taller plants and size increment indicating pleiotropic gene effects or close linkage. The phenotypic effects of the individual QTLs were mostly moderate in terms of phenotypic variance explained. However, a considerable amount of the genetically determined variation was explained by QTLs for stomatal density (from 63.6% to 94.4%). Especially, the QTL on linkage group 11 had a strong and highly significant effect on stomatal densities and growth parameters in all years suggesting a major QTL on this linkage group. The importance to analyse the genetic variation controlling complex adaptive traits in keystone species as oaks is discussed with regard to a better understanding of the reactions of ecosystems to global change.