Saving green ash
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In: Sniezko, Richard A.; Man, Gary; Hipkins, Valerie; Woeste, Keith; Gwaze, David; Kliejunas, John T.; McTeague, Brianna A., tech. cords. 2017. Gene conservation of tree species—banking on the future. Proceedings of a workshop. Gen. Tech. Rep. PNW-GTR-963. Portland, OR: U.S. Department of Agriculture, Forest Service, Pacific Northwest Research Station: 102-110.
The emerald ash borer (EAB, Agrilus planipennis) continues to kill ash trees in North America at an alarmingly fast pace. Although EAB is a threat to all species of ash (Fraxinus) in the United States, green ash (F. pennsylvanica) is among the most susceptible. Among the most commonly planted landscape trees in the United States, green ash is also an important species in riparian forests, rural agricultural systems and urban woodlands. Within 4 to 6 years from the time of first detection, the damage caused by EAB larval feeding can kill 100 percent of the green ash trees in a stand. Green ash is genetically incompatible with EAB-resistant Asian ash species, ruling out a simple backcrossing program to transfer resistance from species. However, a small number of green ash trees (~0.05 percent) have survived long term EAB attack. Careful testing of grafted clones of these “lingering ash” selections provides compelling evidence of a defensive response against EAB. The defenses lingering ash trees possess enable longer survival, but do not prevent premature death. Individual lingering ash trees employ different types of defense responses. Combining these defenses through breeding is expected to produce progeny that combat EAB more effectively than the original parent trees and presumably allow for long-term survival. However, if we do not act now to prevent the death of lingering ash, we will risk losing this invaluable genetic variation forever. An interdisciplinary strategy that combines long-term monitoring to identify lingering ash, wise application of genomic tools, and an EAB resistance breeding program will rescue an irreplaceable genetic resource and provide an accelerated route to the restoration of this important species.
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Romero-Severson, J.; Koch, Jennifer L. 2017. Saving green ash. In: Sniezko, Richard A.; Man, Gary; Hipkins, Valerie; Woeste, Keith; Gwaze, David; Kliejunas, John T.; McTeague, Brianna A., tech. cords. 2017. Gene conservation of tree species—banking on the future. Proceedings of a workshop. Gen. Tech. Rep. PNW-GTR-963. Portland, OR: U.S. Department of Agriculture, Forest Service, Pacific Northwest Research Station: 102-110.