Application of Molecular Genetic Tools for Threat Assessment in Forest Ecosystems
Ned B. Klopfenstein, Mee-Sook Kim, Detlev R. Vogler, Bryce A. Richardson, Jane E. Stewart, and Paul J. Zambino
USDA Forest Service Rocky Mountain Research Station (1-2,4-6), Washington State University Department of Plant Pathology (4), USDA Forest Service Pacific Southwest Research Station (3)
Molecular genetic tools (e.g., genetic markers, DNA sequencing, and genomics) provide powerful methods for molecular diagnostics, genetic mapping, DNA fingerprinting, phylogenetic analysis, and population genetics of trees, pathogens, arthropods, invasive plants, and associated organisms in forest ecosystems. Such tools have become invaluable in diverse applications for detecting, assessing, and predicting environmental threats.
In recent years, molecular genetics has yielded a series of diagnostic tools that are essential for identifying, detecting, monitoring, and characterizing forest pathogens. These tools help to identify and monitor the spread of introduced, invasive, or evolving pathogens, and to determine their origins. Among introduced forest pathogens, molecular tools have been used to identify and/or detect Phytophthora ramorum (cause of sudden oak death), Discula destructiva (cause of dogwood anthracnose), Gremmeniella abietina (cause of Scleroderris canker of pines), and Fusarium circinatum (cause of pine pitch canker). Molecular markers have been used to distinguish aggressive races of forest pathogens (e.g., Sphaeropisis sapinea, the cause of diplodia tip blight of pines) and confirm interspecific hybridization among fungi causing poplar leaf rust, Dutch elm disease, Armillaria root rot, and Phytophthora disease of alder. Genetic markers can help identify virulence genes in forest pathogens and delineate pathogenic populations. Molecular genetic tools have been requisite for assessing disease threats, tracking epidemics, and monitoring pathogen change. This information is critical for effective disease management before and after a pathogen has invaded a forest. Similar approaches can be used to characterize arthropods, invasive plants, and nonpathogenic microorganisms associated with decomposition or biological control in forest ecosystems.
Molecular tools also provide essential information for assessing threats to forest trees. Various DNA markers can be used to characterize tree species, tree populations, and individuals. In genetic mapping, correlations between DNA markers and phenotypic traits are identified among progeny of crosses. With tree species, this allows identification of genetic loci controlling disease resistance or other phenotypic traits. At a broader level, genetic markers are useful to examine population structure and genetic diversity within forest tree species. Because genetically distinct tree populations can differ in their phenotypic responses, characterization of tree populations is necessary for meaningful assessment of abiotic and biotic environmental threats.
Recently, approaches that incorporate genetic marker technology, spatial modeling, and Geographic Information System data have been suggested for managing forest threats at the landscape level. Because population genetic structures vary across the environment and populations of forest trees and associated organisms often correspond to geographic features, the focus of management and threat response must be directed at the landscape level. Genetic structure and geographic distribution of pathogens, arthropods, invasive plants, beneficial organisms, and host-tree populations can be compared to site attributes such as temperature, moisture, soil properties, fire history, topographic characteristics, and management practices. Such analyses are critical in development of effective predictive models that will strengthen forest disease risk assessment.
For the near future, one can envision that the use of molecular genetic tools will be rapidly extended to many pathogens, arthropods, invasive plants, host trees, and beneficial microbes in forest ecosystems. Information derived from these molecular genetic tools will expand our understanding of threat assessment in forest management. One future challenge will be to integrate genetic, environmental, and landscape data in searchable databases that will provide end-users with valuable information for diverse applications.
corresponding author:
Ned Klopfenstein
USDA Forest Service
Rocky Mountain Research Station
1221 South Main Street
Moscow, ID 83843
208-883-2310
nklopfenstein@fs.fed.us
Encyclopedia ID: p115
