88-493: The American chestnut ( Castanea dentata ) is a large, fast-growing deciduous tree of the beech family native to eastern North America. As is true of all species in the genus Castanea , the American chestnut produces burred fruit with edible nuts. The American chestnut was once common in its Appalachian Mountain range and was a dominant species in the oak-chestnut forest region of its central and southern range. During
176-466: A Chinese chestnut, the hybrid would then be bred with a normal American chestnut, subsequent breeding would involve a hybrid and an American chestnut or two hybrids, which would increase the genetic makeup of the hybrids primarily American chestnut but still retain the blight resistance of the Chinese chestnut. A backcross breeding program has integrated desirable American chestnut traits with traits from
264-433: A barrier to chestnut restoration and in direct opposition to the program's goals of collaboration. While patent protection is not sought, the non-profit American Chestnut Foundation (TACF) maintains control through a Germplasm Agreement, ensuring authorized use of chestnut germplasm. The agreement safeguards TACF's rights and aligns with the organization's restoration goals. A laboratory error resulted in mistaken use of
352-399: A behavior known as " marcescence " whereby dead leaves are not shed in the fall and remain on the tree until being blown off by the weather. This is caused by incomplete development of the abscission layer. It is mainly seen in the seedling and sapling stage, although mature trees may have marcescence of leaves on the lower branches. A number of deciduous plants remove nitrogen and carbon from
440-760: A common tree over a range from Maine and southern Ontario to Mississippi , and from the Atlantic coast to the Appalachian Mountains and the Ohio Valley . Within its range, the American chestnut was the dominant timber of mountain ridges and sandstone soils. Along the Blue Ridge Mountains of North Carolina, the American chestnut dominated the area above the range of the Eastern hemlock and below 1,500 meters. In Western Maryland ,
528-451: A defective grade of wood that has insect damage, having been sawn from long-dead, blight-killed trees. This "wormy" wood has since become fashionable for its rustic character. Deciduous In the fields of horticulture and botany , the term deciduous ( / d ɪ ˈ s ɪ dʒ u . ə s / ) means "falling off at maturity" and "tending to fall off", in reference to trees and shrubs that seasonally shed leaves , usually in
616-533: A faster rate than oaks. Being rich in tannins , the wood was highly resistant to decay and therefore used for a variety of purposes, including furniture, split-rail fences , shingles, home construction, flooring, piers, plywood , paper pulp , and telephone poles . Tannins were also extracted from the bark for tanning leather. Although larger trees are no longer available for milling, much chestnut wood has been reclaimed from historic barns to be refashioned into furniture and other items. "Wormy" chestnut refers to
704-494: A food source, both for them and the wildlife they hunted, and also as a component in traditional medicine . The January 1888 issue of Orchard and Garden mentions the American chestnut as being "superior in quality to any found in Europe". The wood is straight-grained, strong, and easy to saw and split, and it lacks the radial end grain found on most other hardwoods. The tree was particularly valuable commercially since it grew at
792-602: A greater rate of transpiration (and hence CO 2 uptake as this occurs when stomata are open) during the summer growth period. The deciduous characteristic has developed repeatedly among woody plants. Trees include maple , many oaks and nothofagus , elm , beech , aspen , and birch , among others, as well as a number of coniferous genera , such as larch and Metasequoia . Deciduous shrubs include honeysuckle , viburnum , and many others. Most temperate woody vines are also deciduous, including grapes , poison ivy , Virginia creeper , wisteria , etc. The characteristic
880-427: A host, and while the oak itself is unaffected, American chestnuts nearby will succumb to the blight in approximately a year or more. In addition, the hundreds of chestnut stumps and "living stools" dotting eastern woodlands may still contain active pathogens. It is considered extirpated from Florida and Illinois . The reduced population of American chestnuts directly impacted many species of insects that relied upon
968-533: A hybrid between the American chestnut and the Allegheny chinquapin from the southern Appalachians. The other lineage of American Chestnut shows a gradual loss of genetic diversity along a Northward vector, indicating possible expansion of range following the most recent Glacial Maximum during the Wisconsin glaciation . Ozark chinkapin , which is typically considered either a distinct species ( C. ozarkensis ) or
SECTION 10
#17327798549771056-490: A low level under basal conditions, but elevates to high levels under conditions of wounding or tissue infection. In laboratory bioassays, win3.12-OxO lines showed elevated disease tolerance similar to that exhibited by blight-resistant Chinese chestnut. American chestnut ( C. dentata ) is susceptible to ink disease , particularly in the southern part of its natural range. Unlike American chestnut, Japanese chestnut ( C. crenata ) exhibits resistance to Phytophthora cinnamomi ,
1144-455: A patent on the project's transgenic lines was to allow the plant to be more accessible for conservationists and members of the public. Powell posits that a patent would constrain the spread of the oxalate oxidase transgene into American chestnut populations by limiting the ability to freely plant transgenic trees and cross the trees with surviving American chestnuts or the hybrids produced in the backcross program. Powell states that patents would be
1232-467: A spiny, green burr, each lined in a tan velvet. In contrast, the Allegheny chinquapin produces but one nut per burr. Chestnuts are in the Fagaceae family along with beech and oak . Chestnuts are not closely related to the horse chestnut , which is in the family Sapindaceae . Phylogenetic analysis indicates a westward migration of extant Castanea species from Asia to Europe to North America, with
1320-439: A standard lethal strain of the blight fungus and measured growth of the cankers. Chestnuts with no resistance to blight make rapid-growing, sunken cankers that are deep and kill tissue right to the wood. Resistant chestnuts make slow-growing, swollen cankers that are superficial: live tissue can be recovered under these cankers. The level of blight resistance is judged by periodic measurement of cankers. Grafts from large survivors of
1408-410: A strong resistance, the American chestnut and Allegheny chinquapin have little resistance. The airborne bark fungus spread 50 mi (80 km) a year and in a few decades girdled and killed more than three billion American chestnut trees. Salvage logging during the early years of the blight may have unwittingly destroyed trees that had high levels of resistance to the disease and thus aggravated
1496-559: A student at Miami University , and to date has planted over 5,000 trees. In 2005, a hybrid tree with mostly American genes was planted on the lawn of the White House . A tree planted in 2005 in the tree library outside the USDA building was still very healthy seven years later; it contains 98% American chestnut DNA and 2% Chinese chestnut DNA. This tree contains enough Chinese chestnut DNA that encodes for systemic resistance genes to resist
1584-723: A subspecies of the Allegheny chinquapin ( C. pumila subsp. ozarkensis ), may be ancestral to both the American chestnut and the Allegheny chinquapin. A natural hybrid of C. dentata and C. pumila has been named Castanea × neglecta . The American chestnut population was reduced to 1–10% of its original size as a result of the chestnut blight and has not recovered. The surviving trees are "frozen in time" with shoots re-sprouting from survivor rootstock but almost entirely undergoing blight-induced dieback without producing chestnuts. Unexpectedly, American chestnut appears to have retained substantial genetic diversity following
1672-530: Is backcrossing blight-resistant Chinese chestnut into American chestnut trees, to recover the American growth characteristics and genetic makeup, and then finally intercrossing the advanced backcross generations to eliminate genes for susceptibility to blight. The first backcrossed American chestnut tree, called "Clapper", survived blight for 25 years, and grafts of the tree have been used by The American Chestnut Foundation since 1983. The Pennsylvania chapter of The American Chestnut Foundation, which seeks to restore
1760-431: Is monoecious , and usually protandrous producing many small, pale green (nearly white) male flowers found tightly occurring along 6 to 8 inch long catkins . The female parts are found near the base of the catkins (near twig) and appear in late spring to early summer. Like all members of the family Fagaceae , American chestnut is self-incompatible and requires two trees for pollination , which can be with other members of
1848-606: Is a deciduous woody shrub found in Japan . Forests where a majority of the trees lose their foliage at the end of the typical growing season are called deciduous forests. These forests are found in many areas worldwide and have distinctive ecosystems, understory growth, and soil dynamics. Two distinctive types of deciduous forests are found growing around the world. Temperate deciduous forest biomes are plant communities distributed in North and South America, Asia, Southern slopes of
SECTION 20
#17327798549771936-700: Is completed (marked by the transition from bright green spring leaves to dark green summer ones) the chlorophyll level in the leaves remains stable until cool temperatures arrive in autumn. When autumn arrives and the days are shorter or when plants are drought-stressed, the chlorophyll steadily breaks down, allowing other pigments present in the leaf to become apparent and resulting in non-green colored foliage. The brightest leaf colors are produced when days grow short and nights are cool, but remain above freezing. These other pigments include carotenoids that are yellow, brown, and orange. Anthocyanin pigments produce red and purple colors, though they are not always present in
2024-584: Is considered an effective control method for the Chinese gall wasp. There are now established populations of Torymus sinensis in North America. American chestnuts were a common part of the forest canopy in southeast Michigan . Although large trees are currently rare east of the Mississippi River , they exist in pockets in the blight-free West, where the habitat was agreeable for planting: settlers took seeds of American chestnut with them in
2112-675: Is continuing to pursue deregulation. American Chestnut Cooperators' Foundation (ACCF) is not using crosses with Asian species for blight resistance, but intercrossing among American chestnuts selected for native resistance to the blight, a breeding strategy described by the ACCF as "All-American intercrosses". John Rush Elkins, a research chemist and professor emeritus of chemistry at Concord University , and Gary Griffin, professor of plant pathology at Virginia Tech , think there may be several different characteristics which favor blight resistance. Both Elkins and Griffin have written extensively about
2200-400: Is formed between the leaf petiole and the stem. This layer is formed in the spring during active new growth of the leaf; it consists of layers of cells that can separate from each other. The cells are sensitive to a plant hormone called auxin that is produced by the leaf and other parts of the plant. When auxin coming from the leaf is produced at a rate consistent with that from the body of
2288-486: Is found in Europe and Oceania. More recently, it has been reported in North America. The Chinese gall wasp attacks all Chestnut species and causes heavy damage. As this species of wasp is a threat to saplings, and is now widely-present in Eastern North American forests, it is a potential problem for reintroduction of the American chestnut. The Chinese parasitoid chalcid wasp Torymus sinensis Kamijo
2376-533: Is not to be confused with sun scald , where winter sun reflects off of snow, warming the bark on the sun-facing trunk (this is the south-facing trunk in the Northern Hemisphere). This snow-reflected sunlight repeatedly warms and thaws the trunk during the day, resulting in vulnerability of the bark and cambium to freezing cold temperatures during the subsequent night, eventually resulting in bark cankers that resemble chestnut blight. Also, sun scald makes
2464-530: Is useful in plant identification; for instance in parts of Southern California and the American Southeast , deciduous and evergreen oak species may grow side by side. Periods of leaf fall often coincide with seasons: winter in the case of cool-climate plants or the dry-season in the case of tropical plants, however there are no deciduous species among tree-like monocotyledonous plants, e.g. palms , yuccas , and dracaenas . The hydrangea hirta
2552-508: The Castanea genus. The pollen of the American chestnut is considered a mild allergen. The American chestnut is a prolific bearer of nuts , with inflorescence and nut production in the wild beginning when a tree is 8 to 10 years old. American chestnut burrs often open while still attached to the tree, around the time of the first frost in autumn, with the nuts then falling to the ground. American chestnut typically have three nuts enclosed in
2640-512: The Chinese chestnut , achieving intermediate resistance to Cryphonectria parasitica and Phytophthora cinnamomi in the hybrid genome. The B3F3 strain, a product of backcrossing and intercrossing with selection for blight resistance, is approximately 94% American chestnut and 6% Chinese chestnut and has been planted experimentally in Maryland in an orchard. Hypovirus is the only genus in
2728-632: The Columbian exchange of pathogens . While the Columbian exchange moved valuable crops between the Americas, Europe and Asia, there was also a downside, as the rapid introduction of invasive and unfamiliar pathogens resulted in serious damage or extinction of some host species. Prior to the Chestnut blight, the American chestnut was a dominant tree in the ecosystem of the eastern deciduous forest. It
American chestnut - Misplaced Pages Continue
2816-598: The SUNY College of Environmental Science and Forestry created the Darling 58 cultivar of American chestnut by inserting the oxalate oxidase gene from wheat into the genome of an American chestnut. When expressed in the vascular cambium of the Darling 58 cultivar, the oxalate oxidase enzyme degrades the oxalic acid produced by the chestnut blight, reducing damage to the vascular cambium and resisting girdling of
2904-464: The University of Minnesota in the 1970s. Burnham, a professor emeritus in agronomy and plant genetics who was considered one of the pioneers of maize genetics, realized that experiments conducted by the USDA to cross-breed American chestnuts with European and Asian chestnuts erroneously assumed that a large number of genes were responsible for blight resistance, while it is currently believed
2992-553: The autumn ; to the shedding of petals , after flowering; and to the shedding of ripe fruit . The antonym of deciduous in the botanical sense is evergreen . Generally, the term "deciduous" means "the dropping of a part that is no longer needed or useful" and the "falling away after its purpose is finished". In plants, it is the result of natural processes. "Deciduous" has a similar meaning when referring to animal parts, such as deciduous antlers in deer , deciduous teeth (baby teeth) in some mammals (including humans); or decidua ,
3080-456: The dry season or other seasons, depending on variations in rainfall . The converse of deciduous is evergreen , where foliage is shed on a different schedule from deciduous plants, therefore appearing to remain green year round because not all the leaves are shed at the same time. Plants that are intermediate may be called semi-deciduous ; they lose old foliage as new growth begins. Other plants are semi-evergreen and lose their leaves before
3168-503: The foliage before they are shed and store them in the form of proteins in the vacuoles of parenchyma cells in the roots and the inner bark. In the spring, these proteins are used as a nitrogen source during the growth of new leaves or flowers. Plants with deciduous foliage have advantages and disadvantages compared to plants with evergreen foliage. Since deciduous plants lose their leaves to conserve water or to better survive winter weather conditions, they must regrow new foliage during
3256-434: The passenger pigeon . Black bears were also known to eat the nuts to fatten up for the winter. The American chestnut also contains more nitrogen , phosphorus , potassium and magnesium in its leaves than other trees that share its habitat, so they return more nutrients to the soil which helps with the growth of other plants, animals, and microorganisms . The American chestnut is preferred by some avian seed hoarders, and
3344-620: The 19th century. Huge planted chestnut trees can be found in Sherwood, Oregon , as the Mediterranean climate of the West Coast discourages the fungus, which relies on hot, humid summer weather. American chestnut also thrives as far north as Revelstoke, British Columbia . At present, it is believed that survival of C. dentata for more than a decade in its native range is almost impossible. The fungus uses various oak trees as
3432-400: The American chestnut comprised 50% of ridge timber and 36% of forested slopes. The tree's abundance was due to a combination of rapid growth, relative fire resistance, and a large annual nut crop, in comparison to oaks, which do not reliably produce sizable numbers of acorns every year. Fire was common in the pre-blight ecosystem of the American chestnut, perhaps in part due to unique traits of
3520-462: The American chestnut more closely related to the Allegheny chinquapin ( Castanea pumila v. pumila ) than to European or Asian clades . The genomic range of chestnuts can be roughly divided into a clinal pattern of northeast, central, and southwest populations, with southwest populations showing greatest diversity, reflecting an evolutionary bottleneck likely due to Quaternary glaciation . Two lineages of American chestnut have been identified, one
3608-564: The American chestnut to the forests of the Mid-Atlantic states , has planted over 22,000 trees. The Surface Mining Control and Reclamation Act of 1977 requires owners of abandoned coal mines to cover at least 80 percent of their land with vegetation. While many companies planted invasive grasses, others began funding research on planting trees, because they can be more cost-effective, and yield better results. Keith Gilland began planting American chestnut trees in old strip mines in 2008 as
American chestnut - Misplaced Pages Continue
3696-491: The American chestnut. They believe that by making intercrosses among resistant American chestnuts from many locations, they will continue to improve upon the levels of blight resistance to make an American chestnut that can compete in the forest. Griffin, who has been involved with American chestnut restoration for many years, developed a scale for assessing levels of blight resistance, which made it possible to make selections scientifically. He inoculated five-year-old chestnuts with
3784-484: The Cast_Gnk2-like gene and the oxalate oxidase gene may provide a means of developing genetically modified American chestnut trees resistant to both the chestnut blight and to ink disease. The American Chestnut Research and Restoration Project at SUNY-ESF is not pursuing intellectual property (IP) protection through patents. Dr William Powell , the project's Co-Director, states that the decision to not pursue
3872-545: The Darling 54 cultivar instead of the Darling 58 cultivar in some field trials. TACF and colleagues have also reported decreased growth rates, and poor heritability of resistance of the Darling 58 cultivar. In response, the American Chestnut Foundation withdrew its support of development of the Darling 58 cultivar in December 2023. The American Chestnut Research & Restoration Program at SUNY ESF
3960-635: The Darling 58 variant has been submitted. If approved, these trees could be the first genetically modified forest trees released in the wild in the United States. In 2022, the SUNY ESF group has developed transgenic American chestnut trees incorporating both the oxalate oxidase transgene from wheat and the win3.12 promoter transgene from the necklace poplar . Unlike the CAMV 35S promoter which acts at all times, this poplar promoter drives OxO expression at
4048-466: The European sweet chestnut ( C. sativa ), Chinese chestnut ( C. mollissima ), and Japanese chestnut ( C. crenata ). Castanea dentata can be distinguished by a few morphological traits, such as petiole length, nut size and number of nuts per burr, leaf shape , and leaf size, with leaves being 14–20 cm (5.5–8 in) long and 7–10 cm (3–4 in) broad—slightly shorter and broader than
4136-844: The Himalayas, Europe and for cultivation purposes in Oceania. They have formed under climatic conditions which have great seasonable temperature variability. Growth occurs during warm summers, leaf drop in autumn, and dormancy during cold winters. These seasonally distinctive communities have diverse life forms that are impacted greatly by the seasonality of their climate, mainly temperature and precipitation rates. These varying and regionally different ecological conditions produce distinctive forest plant communities in different regions. Tropical and subtropical deciduous forest biomes have developed in response not to seasonal temperature variations but to seasonal rainfall patterns. During prolonged dry periods
4224-641: The Southeastern US and at the later time when chestnut blight struck, the range of C. dentata may have already been reduced. The potential range of blight-resistant American chestnuts is substantially reduced if those chestnuts are susceptible to ink disease. Further, the range of this pathogen will extend northward as the climate warms, which may further limit the potential range of the American chestnut. Potassium phosphonate has been found to induce resistance to infection of C. sativa by both inhibiting Phytophthora species directly and by improving
4312-471: The United States. Japanese chestnut was inadvertently introduced into the United States by Thomas Hogg in 1876 and planted on the property of S. B. Parsons in Flushing, New York . The Japanese chestnut has narrow leaves, smaller than either American chestnut or sweet chestnut, with small, sharply-pointed teeth and many hairs on the underside of the leaf and is the most blight-resistant species. The chestnut
4400-448: The below-ground components such as the root systems. It was recorded in the 1900s that the chestnut blight would commonly reinfect any novel stems that grew from the stumps, therefore maintaining a cycle that would prevent the American chestnut tree from re-establishing. However, some American chestnut trees have survived because of a small natural resistance to the chestnut blight. The high density of American chestnuts within its range and
4488-752: The blight epidemic were evaluated following inoculations, and controlled crosses among resistant American chestnut trees were made beginning in 1980. The first "All-American intercrosses" were planted in Virginia Tech's Martin American Chestnut Planting in Giles County, Virginia , and in Beckley, West Virginia . They were inoculated in 1990 and evaluated in 1991 and 1992. Nine of the trees showed resistance equal to their parents, and four of these had resistance comparable to hybrids in
SECTION 50
#17327798549774576-519: The blight. This is essential for restoring the American chestnut trees into the Northeast. The Northern Nut Growers Association (NNGA) has also been active in pursuing viable hybrids. From 1962 to 1990, Alfred Szego and other members of the NNGA developed hybrids with Chinese varieties which showed limited resistance. Initially the backcrossing method would breed a hybrid from an American chestnut nut and
4664-439: The brown skin to access the yellowish-white edible portion. The nuts were commonly fed on by various types of wildlife and was also in such a high abundance that they were used to feed livestock by farmers, by allowing those livestock to roam freely into the forests that were predominantly filled with American chestnut trees. The American chestnut tree was important to many Native American tribes in North America as it served as
4752-405: The calamity. New shoots often sprout from the roots when the main stem dies, so the species has not yet become extinct. However, the stump sprouts rarely reach more than 6 m (20 ft) in height before blight infection returns, so the species is classified as functionally extinct since the chestnut blight only actively kills the above ground portion of the American chestnut tree, leaving behind
4840-460: The damaged bark vulnerable to invasion by pathogens. Before the onset of chestnut blight and prior to 1824, an epidemic of ink disease struck American chestnuts, most likely brought to the southern United States on Cork oak trees imported from Portugal . This fungal pathogen is known to also kill the roots and collars of several Castanea species, including the European species sweet chestnut ( Castanea sativa ). It affected primarily chestnuts in
4928-428: The earliest trees to lose their leaves in the fall. In sub-Arctic climates such as Alaska , leaves begin turning colors as early as August. However, for most temperate regions it takes place in late September through early November and in subtropical climates such as the southern US, it may be November into December. Leaf drop or abscission involves complex physiological signals and changes within plants. When leafout
5016-772: The early to mid-20th century, American chestnut trees were devastated by chestnut blight , a fungal disease that came from Japanese chestnut trees that were introduced into North America from Japan . It is estimated that the blight killed between three and four billion American chestnut trees in the first half of the 20th century, beginning in 1904. Few mature American chestnuts exist within its former range, although many stumps and root systems continue to send up saplings. Most of these saplings get infected by chestnut blight, which girdles and kills them before they attain maturity. There are hundreds of large (2 to 5 ft (0.6 to 1.5 m) in diameter) American chestnuts outside its historical range, some in areas where less virulent strains of
5104-642: The fall months and the Western United States as it has more evergreen and fewer deciduous plants, combined with the West Coast and its maritime climate. ( See also : Autumn leaf color ) Most of the Southern Hemisphere lacks deciduous plants due to its milder winters and smaller landmass, most of which is nearer the equator with only far southern South America and the southern island of New Zealand producing distinct fall colors. The beginnings of leaf drop starts when an abscission layer
5192-518: The family Hypoviridae . Members of this genus infect fungal pathogens and reduce their ability to cause disease (hypovirulence). In particular, the virus infects Cryphonectria parasitica , the fungus that causes chestnut blight, which has enabled infected trees to recover from the blight. The use of hypovirulence to control blight originated in Europe where the fungal virus spread naturally through populations of European chestnuts . The reduced ability of
5280-591: The flowers can be damaged by frost or, in dry season regions, result in water stress on the plant. Spring leafout and fall leaf drop are triggered by a combination of daylight and air temperatures. The exact conditions required will vary with the species, but generally more cold-tolerant genera such as Salix will leaf-out earlier and lose their leaves later, while genera such as Fraxinus and Juglans can only grow in warm, frost-free conditions so they need at least 13 hours of daylight and air temperatures of around 70 °F (21 °C) to leaf out. They will be among
5368-426: The foliage is dropped to conserve water and prevent death from drought. Leaf drop is not seasonally dependent as it is in temperate climates. It can occur any time of year and varies by region of the world. Even within a small local area there can be variations in the timing and duration of leaf drop; different sides of the same mountain and areas that have high water tables or areas along streams and rivers can produce
SECTION 60
#17327798549775456-467: The fungal pathogen that causes ink disease. The mechanism of resistance of C. crenata to Phytophthora cinnamomi may derive from its expression of the Cast_ Gnk2 -like gene (99.6% identical with A0A8J4V9V8 ). Transgenic modification of C. dentata with the Cast_Gnk2-like gene may provide a mechanism for developing American chestnut trees resistant to Phytophthora cinnamomi . Stacking of
5544-421: The fungus to cause disease allowed the European chestnut to regenerate, creating large stands of trees. Hypovirulence has also been found in North America, but has not spread effectively. The "Arner Tree" of Southern Ontario is one of the best examples of naturally occurring hypovirulence. It is a mature American chestnut that has recovered from severe infections of chestnut blight. The cankers have healed over and
5632-554: The gene for wheat oxalate oxidase enzyme, which breaks down the oxalic acid produced by the blight fungus, preventing the death of the tree. When pollen of transgenic fathers fertilizes an ovule of a native mother in the field, those resulting seedlings that express the oxalate oxidase enzyme show growth similar to non-transgenic full siblings, indicating that the transgene does not impede growth under field conditions. The modified chestnut does not affect survival, pollen use, or reproduction of bumble bees . A deregulation petition for
5720-403: The host response, inducing resistance to lesions in phloem tissue and formation of callus. Whether or not this effect would occur in C. dentata is uncertain. Brown nut rot is a destructive plant disease caused by the primary agent Gnomoniopsis castaneae and afflicting Castanea species. This pathogen also causes mild disease or exists as an endophyte in other hardwoods. The disease
5808-417: The humid maritime climate and lower overall species diversity . It is also a factor that the continental United States and southern Canada are at a lower latitude than northern Europe, so the sun during the fall months is higher and stronger. This combination of strong sun and cool temperatures leads to more intense fall colors. The Southern United States also has poor fall colors due to warm temperatures during
5896-407: The lack of natural immunity allowed the blight to spread quickly and cause infection and die-off in nearly every tree exposed. Early attempts to treat chestnut blight were both chemical, such as the use of fungicides , and physical, such as removing infected limbs through tree surgery and the removal of infected trees from cultivated and wild stands. Quarantine measures were also put into place, with
5984-552: The late 19th century. Chestnut blight was first noticed on American chestnut trees in what was then the New York Zoological Park, now known as the Bronx Zoo , in the borough of The Bronx , New York City , in 1904, by chief forester Hermann Merkel. Merkel estimated that, by 1906, blight had infected 98 percent of the chestnut trees in the borough. While Asian chestnut species evolved with the blight and developed
6072-587: The later support of the Plant Quarantine Act , which was an attempt to prevent the importation of other potential plant pathogens. These attempts to contain the spread of chestnut blight were unsuccessful; the devastation of the species was worsened because the chestnut blight resulted in isolation of remaining specimens, resulting in asexual propagation of many isolated American chestnuts, low genetic diversity of stands of American chestnuts and consequent vulnerability to extirpation . Chestnut blight
6160-470: The leaves. Rather, they are produced in the foliage in late summer, when sugars are trapped in the leaves after the process of abscission begins. Parts of the world that have showy displays of bright autumn colors are limited to locations where days become short and nights are cool. The New England region of the United States and southeastern Canada tend to produce particularly good autumn colors for this reason, with Europe producing generally poorer colors due to
6248-418: The moderately blight-resistant Chinese chestnut , then backcrossing with the American chestnut, with the goal of retaining most of its genes. Castanea dentata is a rapidly-growing, large, deciduous hardwood eudicot tree. Pre-blight sources give a maximum height of 100 feet (30 m), and a maximum circumference of 13 feet (4.0 m). Post-blight sources erroneously report a greater maximum size of
6336-412: The next growing season, retaining some during winter or dry periods. Many deciduous plants flower during the period when they are leafless, as this increases the effectiveness of pollination . The absence of leaves improves wind transmission of pollen for wind-pollinated plants and increases the visibility of the flowers to insects in insect-pollinated plants. This strategy is not without risks, as
6424-783: The next suitable growing season; this uses resources which evergreens do not need to expend. Evergreens suffer greater water loss during the winter and they also can experience greater predation pressure , especially when small. Deciduous trees experience much less branch and trunk breakage from glaze ice storms when leafless, and plants can reduce water loss due to the reduction in availability of liquid water during cold winter days. Losing leaves in winter may reduce damage from insects; repairing leaves and keeping them functional may be more costly than just losing and regrowing them. Removing leaves also reduces cavitation which can damage xylem vessels in plants. This then allows deciduous plants to have xylem vessels with larger diameters and therefore
6512-465: The number of responsible genes is low. The USDA abandoned their cross-breeding program and destroyed local plantings around 1960 after failing to produce a blight-resistant hybrid. Burnham's recognition of the USDA's error led to him joining with others to create The American Chestnut Foundation in 1983, with the sole purpose of breeding a blight-resistant American chestnut. The American Chestnut Foundation
6600-606: The pathogen are more common, such as the 600 to 800 large trees in Northern Michigan . The species is listed as endangered in Canada under the Species at Risk Act . American chestnuts are also susceptible to ink disease , particularly in the southern part of its native range; this likely contributed to the devastation of the species. Several groups are attempting to create blight-resistant American chestnuts. Scientists at
6688-469: The plant, the cells of the abscission layer remain connected; in autumn, or when under stress, the auxin flow from the leaf decreases or stops, triggering cellular elongation within the abscission layer. The elongation of these cells breaks the connection between the different cell layers, allowing the leaf to break away from the plant. It also forms a layer that seals the break, so the plant does not lose sap. Some trees, particularly oaks and beeches, exhibit
6776-511: The population bottleneck, which is at odds with the limited incidence of blight resistance/tolerance in extant populations. The pre-blight distribution of the American chestnut was restricted to moist, but well-drained, steep slopes with acid loam soils. According to analysis of old forest dust data, the tree was rare or absent in New England prior to 2,500 years before the present, but rapidly established dominance in these forests, becoming
6864-405: The same test. Many ACCF chestnuts have expressed blight resistance equal to or greater than an original blight survivor but so far, only a handful have demonstrated superior, durable blight control. Time will tell if the progeny of these best chestnuts exhibit durable blight resistance in different stress environments. Backcrossing as a treatment for blight was first proposed by Charles Burnham of
6952-427: The species compared with pre-blight, likely due to nostalgia, to interpretations of pre-blight measurements of circumference as being measurements of diameter , and to the misapprehension that pre-blight observations of maximum size represented observations of average size. It is considerably larger than the closely related Allegheny chinquapin ( Castanea pumila ). There are several other chestnut species, such as
7040-435: The sweet chestnut. It has larger and more widely spaced saw-teeth on the edges of its leaves, as indicated by the scientific name dentata , Latin for "toothed". The European sweet chestnut was introduced in the United States by Thomas Jefferson in 1773. The European sweet chestnut has hairy twig tips in contrast to the hairless twigs of the American chestnut. This species has been the chief source of commercial chestnuts in
7128-626: The tree but the cankers do not spread into the growth tissues of the American chestnut tree, thereby providing it with a resistance. The nuts were once an important economic resource in North America , being sold on the streets of towns and cities, as they sometimes still are during the Christmas season (usually said to be " roasting on an open fire " because their smell is readily identifiable many blocks away). Chestnuts are edible raw or roasted, though typically preferred roasted. One must peel
7216-456: The tree continues to grow vigorously. Scientists have discovered that the chestnut blight remaining on the tree is hypovirulent, although isolates taken from the tree do not have the fungal viruses found in other isolates. Trees inoculated with isolates taken from the Arner tree have shown moderate canker control. The cankers of hypovirulent American chestnut trees occur on the outermost tissues of
7304-565: The tree species for survival. Of approximately 60 species that feed upon the American chestnut, seven rely entirely on the American chestnut as a food source. Some of these, like the American chestnut moth , are now extinct or severely reduced in population. Researchers at the State University of New York College of Environmental Science and Forestry (SUNY ESF) have developed the Darling 58 chestnut cultivar. This cultivar expresses
7392-488: The tree, including fire tolerance, highly flammable litter, tall stature, rapid growth, and ability to resprout. Historically, the mean fire return interval was 20 years or less in chestnut-predominant ecologies, with a forest stand pattern that was more open than is currently the case. The American chestnut was an important tree for wildlife, providing much of the fall mast for species such as white-tailed deer , wild turkey , Allegheny woodrat and (prior to its extinction)
7480-459: The trunk. As of 2021, the researchers who developed this cultivar are working toward applying for government permission to make these trees available to the public. If approved, these chestnut trees would be the first genetically modified forest trees released into the wild in the United States. Alternate approaches to developing a blight-resistant cultivar include cross-breeding among partially blight-resistant American chestnuts or crossbreeding with
7568-464: The uterine lining that sheds off after birth. In botany and horticulture , deciduous plants , including trees , shrubs and herbaceous perennials, are those that lose all of their leaves for part of the year. This process is called abscission . In some cases leaf loss coincides with winter—namely in temperate or polar climates . In other parts of the world, including tropical, subtropical, and arid regions, plants lose their leaves during
7656-545: Was particularly important as a food source during years where the oak mast failed. The functional extinction of the American chestnut may have resulted in the extinction of some of the tree's host-specialist insect associates, including the Greater Chestnut Weevil . The appearance of invasive pathogens of the American Chestnut into the eastern deciduous forest ecosystem is just one instance of
7744-449: Was said that a squirrel could walk from New England to Georgia solely on the branches of American chestnuts. Once an important hardwood timber tree, the American chestnut suffered a catastrophic population collapse due to the chestnut blight , a disease caused by an Asian bark fungus ( Cryphonectria parasitica , formerly Endothia parasitica ). The fungus was introduced when infected Japanese chestnut trees were brought to North America in
#976023