Common Ash (Fraxinus excelsior L.)

Common ash (Fraxinus excelsior L.) has an extensive natural distribution across Europe and extends as far east as the Volga river and south into northern Iran. Country statistics and national programmes show that common ash has major economic and ecological importance in many countries. Genetic improvement has concentrated on tree quality and adaptive traits and more recently on developing resistance to the pathogen Chalara fraxinea which is a severe threat to this species. Data is presented from provenance / progeny trials in Lithuania, France, Belgium, The Netherlands and Romania on genetic variation for adaptive traits, growth and tree quality. There is large variation among and within ash genetic sources for important characters. Estimates for genetic heritability were high for height growth, and stem form and strong site effects were noted for these traits and for stem diameter. The breeding system with regard to genetic diversity, gene flow, hybridisation and inbreeding is reviewed. For breeding, various methodologies regarding mating, testing and selection are discussed. A review on vegetative propagation, including in vitro culture and cryopreservation is presented as useful tools in breeding programmes