PARTNERS: USDA Forest Service Northeastern Area Forest Health Protection, USDA Forest Service Northern Research Station

SUMMARY: Beech bark disease complex (BBD) involves infestation of the American beech tree by the scale insect Cryptococcus fagisuga Lind., which renders the tree susceptible to one of the Nectria species of fungi, resulting in cankering, severe deformation, and death. BBD has spread westward and southward through forests of Canada and the United States and will likely impact American beech throughout its natural range. A small percentage of beech trees, estimated to be between 1 and 5 %, harbor resistance to the scale insect and therefore the disease. Such resistant trees are usually found in “clusters” indicating that they may be clonally related individuals of root sprout origin or closely related full- or half-sibs of seedling origin. As a result, only a portion of the genetic diversity of the species may be represented in the surviving resistant individuals. The researchers’ previous work has shown that American beech has high levels of self-sterility, so in a cluster of clonal trees the primary method of reproduction would be through root sprouting which could, over time, perpetuate only a single genotype. Research has been proposed that would focus on the genetic structure and distribution of genetic diversity across the species range in order to determine the magnitude of the threat of beech bark disease to American beech trees throughout the U.S.

STATUS: Ongoing

PROGRESS: Simple Sequence Repeat (SSR) and Amplified Fragment Length Polymorphism (AFLP) markers have been developed for these genetic diversity studies. They have been used to compare genetic diversity in American beech populations from Massachusetts, Maine, Michigan, and the Monongahela National Forest in West Virginia. In 2008, additional samples will be collected from individual trees in the West Virginia and Maine stands and DNA extractions will be carried out. Screening of additional SSR’s from other species within the beech family will be done to identify additional informative microsatellite loci. Two 96-well plates will be generated containing representatives of both resistant and susceptible individuals from all four stands and used for SSR and AFLP analyses. These data will be used to analyze genetic variation within and between stands and within and between resistant and susceptible individuals. These data will be compared to the original isozyme data reported in previous genetic studies by Houston & Houston (2000).   

LINKS:

USDA Forest Service Northeastern Area Forest Health Protection

USDA Forest Service Northern Research Station

CONTACT: Jennifer Koch, Northern Research Station Research Biologist, jkoch@fs.fed.us or (740) 368-0188