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With the advent of affordable and more accurate third generation sequencing technologies and the associated bioinformatic tools, it is now possible to sequence, assemble, and annotate more species of conservation concern than ever before.Juglans cinerea, commonly known as butternut or white walnut, is a member of the walnut family, native to the Eastern United States and Southeastern Canada. The species is currently listed as Endangered on the IUCN Red List due to decline from an invasive fungus known asOphiognomonia clavigignenti-juglandacearum(Oc-j) that causes butternut canker. Oc-j creates visible sores on the trunks of the tree which essentially starves and slowly kills the tree. Natural resistance to this pathogen is rare. Conserving butternut is of utmost priority due to its critical ecosystem role and cultural significance. As part of an integrated undergraduate and graduate student training program in biodiversity and conservation genomics, we describe the first reference genome forJuglans cinerea. This chromosome-scale 539 Mb assembly was generated from over 100X coverage of Oxford Nanopore long reads and scaffolded with theJuglans mandshuricagenome. Comparisons with sequenced Juglandaceae revealed high levels of synteny and further supportedJ. cinerea’srecent phylogenetic placement. Comparative assessment of gene family evolution revealed a significant number of contracting families, including several associated with biotic stress response.

Butternut is a relatively uncommon hardwood tree native to eastern North America. The species’ abundance has declined over the past 50 years, primarily because of an invasive pathogen (Ophiognomonia clavigignenti-juglandacearum [Oc-j]) and loss of suitable habitat for regeneration. Although genetic diversity of butternut is highest along the southern range edge, genetic diversity rangewide is fairly high, except in small and isolated populations. Although there is little evidence for even moderate resistance in native butternut, hybrids with Japanese walnut, a closely related species, display enough tolerance to infection to persist on the landscape and bear abundant nut crops year after year. Cryostorage of native embryogenic axes has yielded promising initial results as a strategy for gene conservation, but additional action is needed to conserve the remaining native gene pool. We describe a strategy for canker-resistance breeding in butternut using naturally occurring hybrids, hybrids in research orchards, and sources of native trees from as many regions as possible. Forest managers are encouraged to find surviving trees and collect seed for planting in suitable habitat to develop actionable knowledge that will enable the restoration of butternut with enough resistance to be self-sustaining on the landscape.

Forests in North America are threatened by a myriad of native and nonnative pests and pathogens, the latter of which are largely introduced via the international trade of raw wood products and live plants. The early twentieth-century arrival of white pine blister rust (WPBR) (Cronartium ribicola) and chestnut blight (Cryphonectria parasitica) on imported seedlings devastated forests across North America. Invasive species notably affect entire genera. For example, WPBR has now infected all North American five-needle pine (Pinus) species across the entire United States, which has affected species of commercial and noncommercial value and threatened sensitive, high-elevation ecosystems (Sniezko et al. 2011, 2014, Sniezko and Koch 2017).

AbstractReforestation and restoration efforts have traditionally relied on “local” seed sources as planting stock. The term “local” has different meanings in different locales, since no single set of seed-collection zones has yet been widely adopted across the eastern United States. Given concerns about mitigating the effects of climate change, forest managers are increasingly seeking to move seed sources in a process called assisted migration, which would be facilitated if a common set of seed-collection zones were available. We developed a map of 245 seed-collection zones for 37 states by combining two ecologically important layers: plant hardiness zones and ecoregions. These new seed-collection zones should be used by seed collectors and nurseries to describe the origin of seed for plants and trees in the eastern United States. Common garden studies remain the gold standard for determining how far to move seed from any particular seed-collection zone. For species that have not been field-tested, seed movement that is limited either within a seed-collection zone or between adjacent seed-collection zones is a reasonable general guideline.

Quercus rubra half sib progenies (N = 93) expressed high levels of variance for both growth and stem form traits in three locations in Indiana, USA at age 11 or 12. Height, diameter, and volume were measured and sweep, branch angle, forking, and branch retention were rated using a (+ / −) system. Families selected for volume showed no unfavorable increases in sweep or branch angle and only a slight increase in branch retention. Northern red oak (Quercus rubra L.) is the most planted hardwood in the central USA. Red oak seeds from sources with improved growth and form are unavailable in the Central Hardwood Region, in part because the absence of agreed methods for stem form evaluation diminishes the effectiveness of selection. To identify red oak families improved for growth and to determine if a simple + / − rating system could identify red oak families with improved form. We evaluated 93 open-pollinated families of 11 or 12-year-old red oak growing in three sites in central Indiana (USA) for height, diameter, volume, and four traits rated as + / − : sweep, branch angle, forking, and branch retention. Family × location effects were significant for all quantitative traits but not for any binary traits; differences among families were significant for all traits at all sites. Heritabilities for most traits were high. Selection of the top 20 families for volume at each site resulted in no change in population means for sweep or branch angle and only a small increase in the retention of large limbs. A + / − rating system to evaluate hardwood form can help breeders deliver improved red oak to landowners when more complex systems are impractical.

Between the late 1970s and the early 1990s, the USDA Forest Service installed 155 shortleaf pine (Pinus echinata Mill.) progeny tests in national forests across the Southern Region of the United States. Using control-pollinated crosses from the Mount Ida Seed Orchard, 84 of these progeny tests were established in the Ouachita and Ozark-St. Francis National Forests in Arkansas and Oklahoma. Each of these 84 test locations had, on average, 33 full-sibling families representing three local geographic seed sources (East Ouachita, West Ouachita, and Ozark). Though largely abandoned years ago, the progeny tests that remain provided an opportunity to determine if significant genetic and genetic × environment variance exists for performance traits (d.b.h., tree height, and survival) decades after installation. In 2018 and 2019, we remeasured d.b.h. and height and determined survival in 15 fully stocked progeny tests. Family variances were significant (p &lt, 0.01) for both d.b.h. and height but not for survival (p &gt, 0.05). Seed sources differed significantly (p &lt, 0.05) for d.b.h., with more pronounced latitudinal differences. Additionally, we determined that individual tree and full-sibling family mean heritabilities were moderate (0.15 and 0.72, respectively, for d.b.h and 0.09 and 0.41, for height), suggesting relatively high genetic to environmental variation and good potential for genetic improvement. We also found that shortleaf pine families were broadly adapted in this region since family-by-test variances were non-significant (p &gt, 0.05).

Eastern white pine (EWP), Pinus strobus L., is an iconic forest tree in the north woods of eastern North America. White pine blister rust, caused by Cronartium ribicola, an invasive pathogen, entered North America in the early 20th century and infected all five-needled pines across the continent. Few genotypes of eastern white pine have demonstrated consistent, elevated resistance to the pathogen, so our objective was to identify additional genotypes with resistance. Since 1970, the USDA Forest Service has identified and grafted over 800 phenotypic plus tree selections from Michigan, Wisconsin and Minnesota. A protocol to artificially inoculate one-year old seedlings was used to screen 228 genotypes along with rust-resistant and susceptible standards across a four-year period, from 2010 to 2013. We identified 25 genotypes, based on survival assessed two years after inoculation, which exceeded the resistant standard. These genotypes will be grafted into new seed orchards to aid reforestation efforts aimed at restoring this keystone species to suitable habitats where regeneration is currently hindered by blister rust on privately-held land, state forests and national forests in the Lake States region.

Climate change is expected to increase winter temperatures in boreal climates. White spruce (Picea glauca (Moench) Voss) is vulnerable to spring frost damage due to its habit of early budbreak, which may be exacerbated or lessened with increasingly warm winters at its southern range edge. We tested the effects of episodic warming during the quiescent stage on budbreak time and growth of seven seed sources grown in a common garden setting in Minnesota, USA. Treatment plots were warmed with infrared lamps for 4 days each in February, March, or February and March to simulate a midwinter thaw. Control plots for each treatment and an overall control were included for comparison. Trees warmed in February experienced a slight delay in spring budbreak, but differences in budbreak time were generally not significant. Terminal growth was significantly and negatively correlated with time of budbreak but not with time to growth cessation. Our results suggest that white spruce is relatively resilient to the effects of intermittent warming but that warming early in the season may delay budbreak time, which is expected to reduce terminal growth.

White spruce is highly valued by the forest products industry in North America. Through tree improvement efforts, selected genotypes can exceed wild sources by 30% in volume. Negative correlations between growth and wood specific gravity have been established, but differences in leaf morphology between high and low performing genotypes are less well understood. We sampled five trees from each of 30 families at each of two locations in a 25-year old progeny test in Minnesota. One wood core was collected from each tree to sample wood specific gravity (WSG), along with a branch collected from the upper crown to examine foliar traits. We confirmed negative correlations between stem volume and WSG, but several families combined high wood volume with only small reductions in WSG. Leaf area ratio and specific leaf area were positively, genetically correlated with volume growth but not correlated with WSG. Increased growth rates of selected genotypes may be attributed, in part, to shifts in allocation to leaves and in leaf morphology that may optimize light interception.

White spruce (Picea glauca) is commonly planted in timberlands of the upper Great Lakes region. Genetically improved seed, sourced from selected genotypes and propagated in seed orchards, is a primary seed source for artificial regeneration. Volume improvements gained by planting selected genotypes of Picea glauca sources range from 9 to 30 %; however, tradeoffs associated with selection for volume are relatively unexplored for allometry and needle traits. Biomass allocation is of particular interest, especially if increased wood production comes at the expense of root allocation. Open-pollinated seedlings from wild and selected genotypes were planted. Sixty seedlings per source were destructively sampled per year after 1, 2, 3, 4, and 5 growing seasons. Roots, stems, and needles were separated, dried and weighed. Tree height and caliper at root collar were measured, along with specific leaf area. Selected genotypes were allometrically similar to wild sources. Tree heights and biomass allocation were similar between sources during years 2–4. By year 5, selected genotypes averaged 30 % more volume and root mass than wild sources but maintained similar allometric ratios. SLA declined with each year and did not differ between sources. Our results suggest that superior volume growth in selected stock is not the result of alterations in biomass allocation or needle morphology: increases in stem mass were associated with tandem increases in root mass.

Eastern white pine is highly susceptible to damage from white pine weevil, and to some extent white pine blister rust, in the northeastern United States. Western white pine has shown resistance to the weevil, but is highly susceptible to blister rust in the West. Objectives of this study were to compare the growth and resistance of eastern and western white pine to damage from the weevil and blister rust and to identify families of western white pine suitable for planting in the East. A field trial containing 76 half-sib families of western white pine and two half-sib families of eastern white pine was established in 1983 at two sites, one each in New York and Maine. After 14 yr, tree height and diameters were measured, and resistance to weevil and rust assessed. Tree height and diameters were significantly greater for eastern white pine than western white pine. Western white pine sustained approximately fourfold less weevil damage at both sites, but was more impacted by rust at one site. Cluster and discriminant analyses were used to group families using three variables: height growth, resistance to weevil, and resistance to blister rust. One single group combined superior height growth with moderate resistance to both pests. Selections made from within these families have the most promise for planting western white pine in the East. North. J. Appl. For. 20(1):19–26.

Decline of black oak (Quercus velutina Lamarck) on New York’s Long Island in the early 1990’s was associated with a cynipid gall wasp on large urban trees. Symptoms included swollen twigs, gnarled branches, fungal cankers, and crown dieback. A study conducted from 1994 to 1996 showed that symptoms occurred on trees in urban and forested areas. Trees with greater incremental diameter growth before the gall wasp outbreak suffered less dieback than those that grew more slowly prior to the outbreak. A series of periodic environmental stress factors, such as drought and defoliation, played an important role in triggering susceptibility and decline in affected trees.