From Using Science to Save the American Chestnut Tree (TACF

Native To: Asia (Anagnostakis 1997) Date of U.S. Introduction: First discovered in 1904 (Anagnostakis 1997) Means of Introduction: Introduced on nursery stock imported from Asia (Anagnostakis 1997) Impact: Fungal disease of chestnut trees (Castanea spp.) that virtually eliminated mature American chestnuts (Castanea dentata) from the U.S. (Griffin 2000) Current U.S. Distribution: Widespread throughout the U.S. Brief History (from Using Science to Save the American Chestnut Tree (TACF)) During the past 100 years, chestnut blight (Cryphonectria parasitica) and ink rot disease (Phytophthora cinnamomi) decimated an estimated four billion American chestnut (Castanea dentata) trees and brought the iconic species to the edge of extinction. Human interference triggered the American chestnut’s demise–and now scientific innovation offers us the best chance to save it. The American chestnut tree was a vital component of the eastern U.S. ecosystem, economy, and landscape. Before the blight, it was an important food source for a wide variety of wildlife and a valuable cash crop for rural communities from Maine to Alabama. As reliable and productive as the American chestnut tree was, it cannot recover fast enough to sustain itself in the wild. That is why The American Chestnut Foundation (TACF) is leading an unprecedented rescue mission. Our species-saving strategy is a powerful combination of traditional breeding, biotechnology, and biocontrol. Since our founding in 1983, the field of genomics and biotechnology has burgeoned in scope and affordability. Based on new insights into the complex inheritance of blight resistance, TACF has charted a new course for our restoration program. We continue to improve the disease tolerance in our traditional breeding program, while embracing innovations which can integrate the mechanisms of disease tolerance at the molecular level. Our approach follows multiple pathways to create a disease tolerant and genetically diverse population of American chestnut that will be adaptable to broad and changing climate. Breeding. Our traditional breeding program is carried out at our research farm in Meadowview, VA, and at more than 500 orchards planted, largely by volunteers and partners, across sixteen TACF chapters throughout the American chestnut’s native range. During the past 36 years, offspring from blight resistant hybrids have been bred with American chestnuts from across the species’ range. Four generations later, our traditional breeding program has produced a genetically diverse population of American chestnut hybrids with improved blight tolerance from Chinese chestnuts (Castanea mollissima). Moving forward, our breeding efforts are focused on further improving blight tolerance and incorporating resistance to Phytophthora cinnamomi, which causes a fatal root rot in chestnuts. We are using genomics to increase the speed and accuracy of selecting trees with the greatest tolerance to chestnut blight and root rot. Biotechnology. The core of our biotechnology program is transgenics. Scientists at the State University of New York, College of Environmental Science and Forestry (SUNY-ESF) discovered that a gene from wheat produces an enzyme, oxalate oxidase (OxO), which enhances blight tolerance significantly. TACF’s breeding program allows us to stack multiple blight resistance genes and increase the proportion of American chestnut genes in the resulting progeny. Biocontrol. The primary biological control method being explored by TACF and its partners is called hypovirulence. Here, the chestnut blight fungus is infected by a virus, thereby sickening the fungus and reducing the ability of chestnut blight fungus to cause lethal infections. Using this method, the natural defenses of the chestnut tree may enable the tree to halt canker growth and ultimately survive an infection. Other organisms are being investigated to further reducing the effect of the chestnut blight fungus.1 Photo: Blight Canker- Via Kendra Collins 1 The American Chestnut Foundation. “Using Science to Save the American Chestnut Tree.” Last modified 2020. https://www.acf.org/science-strategies/3bur/ Native To: Unknown, possibly Asia (Furnier et al. 1999) Date of U.S. Introduction: First detected in 1967, but may have been present before then (Farlee et al. 2010) Means of Introduction: Unknown (Ostry et al. 2004) Impact: Lethal disease of butternut trees (Juglans cinerea) (Farlee et al. 2010) Current U.S. Distribution: Northeastern and Midwestern U.S. Brief History (from An Intraspecific Tree Breeding Program) “During the mid 1960's, over 500 square miles of butternut veneer, and millions of board feet of butternut lumber were cut annually. Today, over 90% of the remaining butternut is infected with a non-native disease called 'butternut canker', and virtually all cutting of butternut has stopped. Butternut canker disease was most likely introduced from Asia, through the St. Lawrence Seaway, into the ports around the Great Lakes and first noticed in the late 1960's. The disease has now spread east and south to the farthest extent of the butternut's native range. Like Chestnut Blight and Dutch Elm Disease, Butternut Canker has effectively eliminated butternut as a thriving tree species within the northeast forest ecosystem. Most butternut dies within 15 years of infection and virtually all known populations of butternut are now infected…The New Hampshire Division of Forests and Lands has created a project to harvest shoots and buds, called 'scion wood', from the few apparently disease resistant trees still alive in New Hampshire. By collecting scions from the few resistant trees, we can graft them to black walnut root stock to create a seed orchard of resistant butternut trees. When we cross pollinate between different resistant trees, within the orchard, it's hoped we will produce resistant seed which can then be out-planted in the native forest environment that butternut once dominated. The process is called 'intraspecific tree breeding'. The project was started in 1996. Since then, we have surveyed more than 3000 possibly resistant trees at over 300 different sites statewide…”2 -Kyle Lombard, New Hampshire Division of Forests and Lands, Forest Health Section 2 Lombard, Kyle “Butternut restoration Project: An Intraspecific Tree Breeding Program.” Last modified 2019. https://www.nh.gov/nhdfl/community/forest-health/butternut-restoration-project.htm Native To: Eastern Russia, Northern China, Japan, and Korea (McCullough and Usborne 2015) Date of U.S. Introduction: 2002 (McCullough and Usborne 2015) Means of Introduction: Arrived accidentally in cargo imported from Asia (McCullough and Usborne 2015) Impact: Ash trees lose most of their canopy within 2 years of infestation and die within 3-4 years (McCullough and Usborne 2015; Poland and McCullough 2006) Brief History (from Biological Control of the Emerald Ash Borer, USFS NRS) In 2002, the emerald ash borer (EAB), Agrilus planipennis (Coleoptera: Buprestidae), an Asian beetle that feeds on ash trees (Fraxinus spp.), was discovered as the cause of widespread ash tree mortality in southeast Michigan and nearby Ontario. The results of subsequent studies showed that EAB was inadvertently introduced near Detroit, Michigan during the 1990s from northeast China, probably in EAB-infested solid-wood packing materials used in international trade. Despite federal and state quarantines that restricts the movement of ash out of infested areas, EAB continues spreading in the U.S. and eastern Canada. Although this beetle spreads naturally by flying short distances, long-distance spread is caused by people moving EAB-infested ash firewood, nursery stock, and timber. The rapid expansion of the EAB infestation across a wide range of climate zones suggests that this invasive beetle will continue spreading throughout the continent… Biocontrol of EAB began in the U.S. in 2007 when APHIS issued permits for the environmental release of three hymenopteran parasitoid species of EAB from China to EAB- infested ash stands in southern Michigan. These EAB biocontrol agents are: an egg parasitoid, Oobius agrili (Encyrtidae) (Fig.1) and two larval parasitoids, Tetrastichus planipennisi (Eulophidae) (Fig. 2) and Spathius agrili (Braconidae) (Fig. 3). In 2015, another EAB larval parasitoid, Spathius galinae (Braconidae) (Fig. 4) from the Russian Far East, was approved for release because S. agrili did not establish in northern regions.3 3 USDA Forest Service Northern Research Station. “Biological Control of the Emerald Ash Borer.” Last modified July 31, 2019. https://www.nrs.fs.fed.us/disturbance/invasive_species/eab/control_management/biological_control/ Native To: Japan (Orwig et al. 2003) Date of U.S. Introduction: Discovered on the West Coast in the 1920s, but it is disputed whether this was an introduced or native population; an introduced population was discovered on the East Coast in the 1950s (Havill et al. 2006; Orwig et al. 2003) Means of Introduction: Accidental (Wallace and Hain 2006) Impact: Destroys Eastern hemlock trees (Tsuga canadensis) (Orwig et al. 2003) Brief History (from Hemlock Woolly Adelgid: A Non-Native Pest of Hemlocks in Eastern North America) It is the single most important pest of hemlocks in eastern North America and has a severe impact on the two susceptible species: eastern hemlock, Tsuga canadensis (L.) Carriere (Pinales: Pinaceae) and Carolina hemlock, Tsuga caroliniana Engelmann (Pinales: Pinaceae). Since the first report of hemlock woolly adelgid in Virginia in 1951, it has been slowly

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