MORRIS, ASHLEY B. Department of Botany, University of Florida, Gainesville, FL 32611. - Assessing the potential for genetic resistance to beech bark disease in Fagus grandifolia Ehrh. (Fagaceae).
In recent years populations of Fagus grandifolia (American
Beech) have been decimated across the speciesí range due to an insect
mediated fungal pathogen complex known as beech bark disease (BBD). As
this disease spreads throughout the range of F. grandifolia,
average mortality within a population is estimated to be as much as
85% (Houston 1979). Houston and Houston (1994) observed resistance in
less than 1% of 325 F. grandifolia trees that they sampled, but
they note that resistant stems often occurred in discrete clumps or
groups, suggesting the possibility of resistance clonal genotypes.
Houston and Houston (1994, 2000) used isozymes in an attempt to
identify resistant genotypes in F. grandifolia and found that
individual stems sharing the same genotype could be either infected or
not infected. It is important to note that allozymes often do not
display adequate levels of variation to resolve genetic identities in
clonal populations (Cruzan 1998, Escaravage 1998, and Waycott 1998).
Whereas allozyme studies are commonly limited to less than 10
polymorphic loci, studies using markers based on DNA variation can
include many times that number of loci for the resolution of
individual genotypes. I used inter-simple sequence repeats (ISSRs) to
investigate the potential of genetic resistance to beech bark disease
in Fagus grandifolia in Great Smoky Mountains National Park.
Clonemates exhibited all possible levels of infection, ranging from
none to greater than 75%, suggesting that genetic resistance is not a
factor in the sites studied.
Key words: beech bark disease, Fagus grandifolia, Great Smoky Mountains National Park, ISSR