Steps toward restoration of butternut Juglans cinerea L. to Southeastern North American forests.
Brosi, Sunshine*,1, Schlarbaum, Scott1, Thompson, Laura1, Anderson, Robert2, van Manen, Frank3, Anagnostakis, Sandra5, 1 The University of Tennessee, Knoxville, Knoxville, TN2 Consulting Forest Pathologist, West Plains, MO3 U. S. Geological Survey, Knoxville, TN5 Connecticut Agricultural Experiment Station, New Haven, CT
ABSTRACT- Butternut Juglans cinerea L., a lesser-known relative of black walnut Juglans nigra L., is a native tree species beneficial for ecosystem diversity, wildlife and valuable for timber in the eastern forests of North America. Populations of butternut are being devastated by butternut canker disease, caused by the exotic fungus Sirococcus clavigignenti-juglandacearum (V.M.G. Nair, Kostichka, and Kuntz). The disease causes multiple branch and stem cankers that eventually girdle trees. Small population sizes, shade intolerance, and lack of regeneration, including vegetative reproduction, combined with the stress of the disease, result in permanent losses of butternut across the native range. Fortunately, healthy, canker-free butternut trees have been found proximal to diseased trees, indicating that they may be resistant, and that a breeding approach could be a feasible strategy for producing resistant butternuts. A successful restoration program requires genetically diverse germplasm and an understanding of site requirements, establishment protocols, and disease resistance. Habitat models developed with a geographic information system have been used to efficiently locate additional trees with putative resistance in the St. Francis National Forest, Mammoth Cave and Great Smoky Mountain National Parks. These models have also identified areas favorable for butternut restoration. Seedlings from an array of butternut selections were planted across a variety of sites in an attempt to identify superior families and investigate factors involved in seedling establishment. Resistance screening plantings have exposed open-pollinated families to heavy disease pressure by planting seedlings under infected butternut trees at various locations. Significant differences in survival, growth, and disease development have been found and offer opportunities to select genotypes for integration into resistance breeding programs to produce canker-resistant, locally-adapted seedlings for use in restoration efforts.
Key words: forestry restoration, invasive pests, Juglans cinerea
All materials copyright The Ecological Society of America (ESA), and may not be used without written permission.