Vegetative Propagation of American Beech Resistant to Beech Bark Disease

Abstract

The objective of this study was to develop vegetative propagation techniques—using tissue culture and grafting—for American beech (Fagus grandifolia) resistant to beech bark disease. Resterilizing the buds after excising bud scales reduced contamination of in vitro cultures derived from dormant buds. Application of a 7-day dark treatment before transferring shoots to the rooting medium improved rooting success. Plantlets gradually acclimatized to nonsterile growth conditions and set buds but failed to survive the dormant period. The application of 6-benzyladenine enhanced sprouting from roots collected from mature trees, but the excised shoots rooted poorly in vitro despite low contamination. Success of grafting scions from mature trees varied among genotypes and differed each year (30% in 2003, 12% in 2004, and 18% in 2005). Applying the growth hormone indole butyric acid to the scion before joining it to the rootstock did not increase grafting success. Survival of grafts was independent of rootstock age (1 or 2 years old). Grafting success increased when scion diameter was slightly larger than rootstock diameter. The rooting of sucker cuttings was successful for only one genotype. Critical steps, in which most failures in the propagation of American beech occur, are identified.