Molecular and Morphological Characterization of Reciprocal F1 Hybrid Ash (Fraxinus excelsior × Fraxinus angustifolia, Oleaceae) and Parental Species Reveals Asymmetric Character Inheritance

AbstractHybridization between Fraxinus excelsior and Fraxinus angustifolia is common. However, identifying hybrids in natural populations is difficult because the closely related parental species share many morphological characters and the inheritance pattern of these characters in hybrids is unknown. We evaluated how morphological characters are inherited and whether morphological and molecular markers can efficiently discriminate artificial first-generation hybrids. Reciprocal F1 hybrids of F. excelsior with F. angustifolia were examined using six microsatellite DNA marker loci and 14 morphological characters. Plants were divided into four groups (F. angustifolia, F. excelsior, the F1 hybrid with F. angustifolia as the maternal parent, and the F1 hybrid with F. excelsior as the maternal parent). The F1 hybrids showed intermediate morphology in most characters, and the range of variation overlapped with the parental species. Canonical discriminant analysis using only the morphological traits separated th...