Biotechnological approaches for the improvement and conservation of alnus glutinosa (L.) gaertner

Abstract

European alder [Alnus glutinosa (L.) Gaertner], also called black alder or European black alder, is a medium-sized tree that is widely distributed throughout Europe. In the few decades, black alder populations have declined drastically, partly as a result of deforestation and the disappearance of riparian habitats but mainly because of alder blight disease, caused by Phytophthora alni. In order to protect these important genetic resources, the existing conservation methods must be improved and new tools developed. Biotechnological methods, particularly in vitro or tissue culture methods, could be beneficial for the large-scale multiplication, improvement and conservation of the species. Axillary shoot proliferation from cultured meristems is the most frequently used method of micropropagation, as it provides genetic stability. Axillary shoot multiplication has been achieved in several species of the genus Alnus. Although most of these reports refer to material of juvenile origin, such as seedlings or young trees, there have been few reports regarding the propagation of mature trees. Plantlets from mature trees of A. glutinosa are obtained and are viable for reintroduction to the natural habitat of the species. The explants used for in vitro multiplication can be stored at 4 °C under dim lighting for up to 18 months. The stored material can be successfully recovered and shows good growth that develops into shoots that are morphologically similar to those of non-stored controls. This technique reduces maintenance requirements and the risk of genetic alterations. Somatic embryogenesis is considered the most efficient in vitro procedure for mass propagation of plants. This technique has been successfully applied to immature zygotic embryos of black alder. This protocol may help to enhance the propagation of A. glutinosa and other alder species and could also provide a regeneration system for future use in genetic manipulation for introducing genes that confer resistance to pathogens such as P. alni. In vitro shoot tips and embryogenic cultures can be successfully cryopreserved by vitrification, indicating that long-term storage of black alder germplasm may be possible. The material could then be safely stored while field tests are undertaken.