ARS Scientists Cryopreserve Pest-Imperiled Ash
Trees By Jan
Suszkiw October 27, 2009
Using cryopreservation methods, Agricultural Research Service (ARS)
scientists have devised a procedure for storing frozen budwood from ash trees
(Fraxinus) and thawing the delicate buds for later use in propagation.
The advance, reported in the journal CryoLetters, should complement
ongoing seed-conservation efforts aimed at preserving the genetic diversity of
America's native ash species, which are susceptible to the emerald ash borer
(EAB), Agrilus planipennis.
Metallic green and 1/2-inch long, this exotic beetle from northern
Asia has killed tens of millions of ash trees in several states since first
being detected near Detroit, Mich., in June 2002. Since then, the EAB has
spread to 12 other states and two Canadian provinces.
The stored budwood samples, along with conserved seed, can serve as a
national source for reintroducing ash trees once the devastation from EAB can
be controlled, according to
Widrlechner, a horticulturist with the ARS
Central Regional Plant Introduction Station in Ames, Iowa. Widrlechner
co-developed the budwood cryopreservation method with plant physiologist
Volk and colleagues at the ARS
Center for Genetic Resources Preservation in Fort Collins, Colo.
Ash trees--among America's most prized shade trees--are at risk in
both managed landscapes and natural forest habitats. Besides the ecological
harm, the loss of ash trees to EAB infestations is of economic concern. Indeed,
numerous forest products are derived from the species, including lumber for
furniture, tool handles and baseball bats.
Building on earlier cryopreservation successes with apple and willow
tissues, the researchers devised a series of preconditioning steps necessary to
store and remove dormant ash budwood from liquid-nitrogen vapor without
significant loss of vigor. In trials, the team successfully grafted 42 to 100
percent of cryopreserved budwood stems onto rootstocks used to generate new
trees of specific clones or cultivars.
The study's storage times ranged from two to 18 months. But according
to Volk, similar procedures used on apples suggest that ash budwood can likely
be cryopreserved for at least 20 years.
ARS is the principal intramural scientific research agency of the
U.S. Department of