Inadequate Cold Tolerance as a Possible Limitation to American Chestnut Restoration in the Northeastern United States

The American chestnut (Castanea dentata (Marshall) Borkh.), once a major component of eastern forests from Maine to Georgia, was functionally removed from the forest ecosystem by chestnut blight (an exotic fungal disease caused by Cryphonectria parasitica (Murr.) Barr), first identified at the beginning of the twentieth century. Hybrid‐backcross breeding programs that incorporate the blight resistance of Chinese chestnut (Castenea mollissima Blume) and Japanese chestnut (Castenea crenata Sieb. & Zuc.) into American chestnut stock show promise for achieving the blight resistance needed for species restoration. However, it is uncertain if limitations in tissue cold tolerance within current breeding programs might restrict the restoration of the species at the northern limits of American chestnut's historic range. Shoots of American chestnut and hybrid‐backcross chestnut (i.e., backcross chestnut) saplings growing in two plantings in Vermont were tested during November 2006, February 2007, and April 2007 to assess their cold tolerance relative to ambient low temperatures. Shoots of two potential native competitors, northern red oak (Quercus rubra L.) and sugar maple (Acer saccharum L.), were also sampled for comparison. During the winter, American and backcross chestnuts were approximately 5°C less cold tolerant than red oak and sugar maple, with a tendency for American chestnut to be more cold tolerant than the backcross chestnut. Terminal shoots of American and backcross chestnut also showed significantly more freezing damage in the field than nearby red oak and sugar maple shoots, which showed no visible injury.     

云南板栗的种质资源

通过对云南省１４个地区（州）７２个县板栗产区的调查与种质收集,观察和测定,基本摸清了全省板栗的分布和种质资源,发现云南省板栗种质多样性十分丰富,坚果总体品质优良,并从生物学和生态地理学上分析该省板栗多样性形成的基础,认为云南省板栗品质兼有暖温带地区板栗的甜糯、美观的色泽以及亚热带地区板栗含水量较高的特点,是我国亚热带板栗分布区的一个独特产区,在调查分析基础上初选出了３０个优良单株。     

The cultivation of<Emphasis Type="Italic"> Castanea sativa</Emphasis> (Mill.) in Europe,from its origin to its diffusion on a continental scale

The history of Castanea sativa (sweet chestnut) cultivation since medieval times has been well described on the basis of the very rich documentation available. Far fewer attempts have been made to give a historical synthesis of the events that led to the cultivation of sweet chestnut in much earlier times. In this article we attempt to reconstruct this part of the European history of chestnut cultivation and its early diffusion by use of different sources of information, such as pollen studies, archaeology, history and literature. Using this multidisciplinary approach, we have tried to identify the roles of the Greek and Roman civilizations in the dissemination of chestnut cultivation on a European scale. In particular, we show that use of the chestnut for food was not the primary driving force behind the introduction of the tree into Europe by the Romans. Apart from the Insubrian Region in the north of the Italian peninsula, no other centre of chestnut cultivation existed in Europe during the Roman period. The Romans may have introduced the idea of systematically cultivating and using chestnut. In certain cases they introduced the species itself; however no evidence of systematic planting of chestnut exists. The greatest interest in the management of chestnut for fruit production most probably developed after the Roman period and can be associated with the socio-economic structures of medieval times. It was then that self-sufficient cultures based on the cultivation of chestnut as a source of subsistence were formed.Electronic Supplementary Material Supplementary material is available in the online version of this article at . A link in the frame on the left on that page takes you directly to the supplementary material.     

Genetic diversity of the sweet chestnut (<Emphasis Type="Italic">Castanea sativa</Emphasis> Mill.) in Central Europe and the western part of the Balkan Peninsula and evidence of marron genotype introgression into wild populations

The sweet chestnut (Castanea sativa Mill.) is a widely spread and important multipurpose tree species in the Mediterranean area, which has played an important role in human history. Natural events, such as glaciations, and human influence played significant roles in the distribution and genetic makeup of the sweet chestnut. In order to better understand how natural and human-mediated past events affected the current genetic diversity and structure of the sweet chestnut, we analysed populations from Central Europe and the western part of the Balkan Peninsula, utilizing ten polymorphic nuclear microsatellite markers. The study revealed the existence of three genetically and, to a large extent, geographically distinct and well-defined groups of sweet chestnut populations. Two not entirely separated groups of populations were detected in the northern part of the studied area and one in the southern. Our results indicate that the genetic structure of sweet chestnut populations in Central Europe and the western part of the Balkan Peninsula is the result of both natural colonization events and significant and lengthy human impact. Furthermore, it has been proven that the gene flow between cultivated/grafted trees’ and wild chestnut stands can influence their genetic structure. However, our results reveal that cultivated-to-wild introgression in the sweet chestnut is dependent on the close proximity of chestnut orchards and naturally occurring populations.     

A missense mutation in the gene for melanocyte-stimulating hormone receptor (MCIR) is associated with the chestnut coat color in horses

The melanocyte-stimulating hormone receptor gene (MC1R) is the major candidate gene for the chestnut coat color in horses since it is assumed to be controlled by an allele at the extension locus. MC1R sequences were PCR amplified from chestnut (e/e) and non-chestnut (E/−) horses. A single-strand conformation polymorphism was found that showed a complete association to the chestnut coat color among 144 horses representing 12 breeds. Sequence analysis revealed a single missense mutation (83Ser → Phe) in the MC1R allele associated with the chestnut color. The substitution occurs in the second transmembrane region, which apparently plays a key role in the molecule since substitutions associated with coat color variants in mice and cattle as well as red hair and fair skin in humans are found in this part of the molecule. We propose that the now reported mutation is likely to be the causative mutation for the chestnut coat color. The polymorphism can be detected with a simple PCR-RFLP test, since the mutation creates a TaqI restriction site in the chestnut allele. Received: 20 May 1996 / Accepted: 31 July 1996     

Effects of transgenic American chestnut leaf litter on growth and survival of wood frog larvae

Biotechnology offers a new approach for the restoration of tree species affected by exotic pathogens; however, nontarget impacts of this novel strategy on other organisms have not been comprehensively assessed. We evaluated the effect of transgenic American chestnut (Castanea dentata) leaf litter on the growth and survival of larval wood frogs (Lithobates sylvaticus), a forest‐dwelling amphibian species widely sympatric with American chestnut, that forage almost entirely on periphyton and litter detritus that accumulate in temporary vernal pools in forests. We reared wood frog larvae on Castanea leaf litter (American chestnut genetically engineered for blight tolerance, nontransgenic American chestnut, Chinese chestnut [Castanea mollissima], and an American–Chinese chestnut hybrid) and litter from two non‐Castanea, nontransgenic “control” tree species, coupled with two levels of supplementary food. We observed no differences in growth or survival of wood frog larvae reared on transgenic versus nontransgenic American chestnut leaves. Without supplementary food, wood frog larvae provided leaves from American chestnut (both types) developed faster and grew larger than those exposed to other leaf litter treatments. Results of this study provide preliminary evidence that (1) American chestnut may have formerly been an important source of food for forest‐dwelling amphibians and (2) transgenic American chestnut litter generated as part of chestnut restoration efforts is unlikely to present direct novel risks to developing amphibian larvae in the forest environment.     

Landscape genetic structure of chestnut (Castanea sativa Mill.) in Spain

The current need for forest conservation and management has driven a rapid expansion of landscape genetics approach. This discipline combines tools from molecular genetics, landscape ecology and spatial statistics and is decisive for improving not only ecological knowledge but also for properly managing population genetic resources. This approach could be appropriate to sweet chestnut (Castanea sativa Mill.), a multipurpose species of great economic importance in the Mediterranean basin and a species considered to be a good model of integration between natural and human-driven distribution of diversity. Sixteen chestnut populations, covering the distribution range of the species in Spain, were analysed using seven microsatellite markers. Results revealed a high level of genetic diversity in Spanish chestnut populations, which in part followed a geographical pattern, although distribution was not homogeneous. Likewise, areas particularly rich in diversity were detected, facilitating the development of a hypothesis about the history of chestnut in Spain. In conclusion, these results provide valuable baseline data for more in-depth studies on chestnut landscape genetics that can contribute to its conservation.     

Treatment of bean cuttings by chestnut extracts during rooting modifies their IAA-oxidase activity

The IAA-oxidase activity in bean cuttings ( Phaseolus vulgaris L. cv. Contender) treated with extracts from juvenile and adult chestnut ( Castanea sativa Mill.) was studied in the light of the effect of the extracts on the rooting activity of some auxins. Extracts from adult chestnut increased IAA-oxidase activity in bean cuttings. Extracts from juvenile chestnut inhibited IAA-oxidase activity only slightly, but substantially reduced the IAA-oxidase activity of bean cuttings pre-treated with adult chestnut extracts. These findings provide evidence that there is a relationship between the IAA-oxidase system and the effect of chestnut extracts on IAA-induced rhizogenesis in bean cuttings.     

Resource limitation in natural populations of phytophagous insects. A long-term study case with the chestnut weevil

The chestnut weevil, Curculio elephas (Gyll.), is a non-outbreaking species whose populations and food resources, the European chestnut, Castanea sativa, can be precisely defined. Thirteen and 17 generations of this insect were studied in two isolated sites. Field observations and experiments allowed us to estimate the absolute abundance, availability and use of chestnuts for weevil oviposition, and the number of weevil females emerging per site. Unavailable chestnuts were defined as the fruits either infested first by the chestnut moth (Cydia splendana) larvae (because of competition between the two species) or those avoided by chestnut weevil females when selecting their egg-laying sites, independently of chestnut moth presence. From a third to a half of the chestnuts were not available on the average for weevil infestation. Only one-fourth, on the average, of those available for oviposition were actually used by chestnut weevil females. Regardless of year and site, the number of available chestnuts per weevil female was higher than that of weevil-infested fruits per female, considering global food resources independently of their temporal variation in quality. However, realized fecundity of weevil females was positively correlated with the mean number of available chestnuts per female. We concluded that food resources can be limiting without being fully exploited by females because of temporal variation in chestnut quality.     

Chromosome-level genome assembly of Japanese chestnut (Castanea crenata Sieb. et Zucc.) reveals conserved chromosomal segments in woody rosids

Japanese chestnut (Castanea crenata Sieb. et Zucc.), unlike other Castanea species, is resistant to most diseases and wasps. However, genomic data of Japanese chestnut that could be used to determine its biotic stress resistance mechanisms have not been reported to date. In this study, we employed long-read sequencing and genetic mapping to generate genome sequences of Japanese chestnut at the chromosome level. Long reads (47.7 Gb; 71.6× genome coverage) were assembled into 781 contigs, with a total length of 721.2 Mb and a contig N50 length of 1.6 Mb. Genome sequences were anchored to the chestnut genetic map, comprising 14,973 single nucleotide polymorphisms (SNPs) and covering 1,807.8 cM map distance, to establish a chromosome-level genome assembly (683.8 Mb), with 69,980 potential protein-encoding genes and 425.5 Mb repetitive sequences. Furthermore, comparative genome structure analysis revealed that Japanese chestnut shares conserved chromosomal segments with woody plants, but not with herbaceous plants, of rosids. Overall, the genome sequence data of Japanese chestnut generated in this study is expected to enhance not only its genetics and genomics but also the evolutionary genomics of woody rosids.     

Exposure to herbivores increases seedling growth and survival of American chestnut (Castanea dentata) through decreased interspecific competition in canopy gaps

The successful development of early stages of blight‐resistant hybrid stock has increased hopes for restoration of American chestnut (Castanea dentata) to eastern North American forests. However, these forests have undergone substantial ecological change in the century since the functional extirpation of American chestnut, and it remains unknown to what extent American chestnut will be able to recolonize contemporary forests. In particular, high densities of white‐tailed deer (Odocoileus virginianus) and competition with mesophytic tree species such as maple (Acer) may impede chestnut regeneration, much as they affect oak (Quercus). We used a split‐plot analysis of variance (ANOVA) design to examine the effects of canopy gaps and herbivory on survival and growth of third generation backcrossed (BC₃) hybrid chestnut seedlings over two growing seasons in central Indiana, U.S.A. Only 4 of 588 (0.7%) seedlings in closed‐canopy plots survived to the end of the study, as opposed to 264 of 589 (45%) seedlings in gap plots. Within the gap treatment, fencing was associated with reduced chestnut survival as well as reduced herbivory and increased cover of non‐chestnut vegetation. Our results indicate that herbivory may indirectly benefit chestnut regeneration by suppressing competition. However, this beneficial effect is likely context‐dependent and additional work is needed to establish the conditions under which it occurs.     

板栗种子发育期间ABA等生理指标与脱水耐性的相关性研究

对板栗种子发育期间胚轴和子叶中部分生理指标的变化以及它们与板栗种子脱水耐性的相关性进行研究.结果表明:随着板栗种子不断发育,在花后80 d胚轴和子叶中ABA、淀粉、可溶性蛋白质量分数同步达到最大值,可溶性糖质量分数达到最低,此时板栗种子的脱水耐性最强,可确定为板栗的最佳采收期.另外,通过相关分析可知,板栗种子在发育期间...     

Heterozygote advantage in the American chestnut, Castanea dentata (Fagaceae)

The American chestnut (Castanea dentata; Fagaceae) was a dominant canopy tree in the Appalachian Mountains of North America. Since the introduction of the chestnut blight fungus (Cryphonectria parasitica; Valsaceae) in America, the American chestnut has been reduced to a predominantly clonal, understory species. Our objective was to determine whether the ecological changes and absence of new recruits have influenced the population genetics of American chestnut. Leaf samples were collected from four populations in southwestern Virginia. Electrophoretic data from five polymorphic loci were used to determine the genetic diversity and population structure of the populations and subpopulations. Growth data and infection status were recorded for one of the populations to determine their relationship with heterozygosity. F statistics revealed a significant amount of differentiation among subpopulations and an excess of heterozygotes within subpopulations. Heterozygous individuals also had higher rates of vegetative growth. The superior performance and excess of heterozygotes suggests that selection favors heterozygous individuals. The prolonged absence of sexual reproduction in C. dentata has allowed subtle fitness differences to accumulate to the extent that they have had significant effects on the genetics of chestnut populations.     

Forest Management and Plant Species Diversity in Chestnut Stands of Three Mediterranean Areas

Over many centuries, chestnut fruits had an important role as food, while chestnut wood was used for local purposes. Today sweet chestnut stands are very common around the western Mediterranean Basin, and it is necessary to analyze the dynamic of plant species diversity in different chestnut stand types (groves and coppices) to guide management strategies that will allow the conservation of biodiversity. Our objective was to analyze consequences on plant species diversity of various management strategies in chestnut stands of three Mediterranean areas, Salamanca (Spain), the Cévennes (France), and Etna volcano (Italy). We found that plant species diversity is different according to management types; it is higher in groves than in coppice stands. We also demonstrated that Castanea sativa cultivated groves were characterized by small heliophillous therophytes. C. sativa abandoned groves, mixed C. sativa–Quercus pyrenaica coppice stands, Q. pyrenaica coppice stands, and young C. sativa coppice stands were characterized by hemicryptophytes with anemochorous dispersal mode and chamaephytes. Medium and old C. sativa coppice stands (that differ by the shoot age) were characterized by phanerophytes with zoochorous dispersal mode. Human perturbations maintain a quite high level of species diversity. In contrast, the abandonment of chestnut stands leads to homogeneous vegetation with decreasing diversity. One solution could be to maintain a landscape mosaic constituted of diverse chestnut stands modified by human activities (groves, cultivated or abandoned, and coppice stands). This could enhance regional plant diversity.     

板栗疫病菌致病力分化的研究

中国板栗(Castanea mollissima Blume)对板栗疫病菌(Cryphonectria parasitica(Murr.)Barr)具有强的抗病力。但近十多年来,我国许多省份均发现有板栗疫病,据调查,广西有19个县市存在栗疫病,有的地方发病还相当严重。为了解释疫病发生的上述情况,并为生产和该病菌的更深入研究提供指导,作者在广西桂林、南宁、柳州、梧州、河池等地收集菌株,对疫病菌致病性的分化进行了研究,现将结果报道如下。 1 材料和方法 1.1 毒力参照菌株 法国已知弱毒株EPF为毒力参照株。 1.2 栗疫病菌的采集、分离和单孢纯化 1.2.1 标本采集:1988年12月～1989年6月,采自广西桂林、南宁、柳州、梧州、河池等地板栗病株。 1.2.2 菌株分离和纯化:将病枝或病树皮,用经灯焰灼烧过的刀片削去表皮,取坏死内皮约5×5mm^2,压于PDA上,28℃,光照培养,产孢后用微块法进行单孢纯化。 1.3     

Ectomycorrhizal characterization of an American chestnut <Emphasis Type="SmallCaps">(</Emphasis><Emphasis Type="Italic">Castanea dentata</Emphasis><Emphasis Type="SmallCaps">)</Emphasis>-dominated community in Western Wisconsin

Circa 1900, a farmer from the eastern US planted 11 American chestnut (Castanea dentata) seeds on a newly established farm near West Salem in western Wisconsin. These trees were very successful, producing a large stand of over 6,000 trees. Since this area is well outside the natural range of chestnut, these trees remained free from chestnut blight until 1987. In the West Salem stand, chestnuts are the dominant species of a mixed forest community, reminiscent of the chestnut–oak ecosystems of pre-1900 Appalachia. To identify putative mycorrhizal associates of chestnut in this unique forest, our approach was twofold: (1) an extensive fruiting body survey was conducted for four seasons that yielded approximately 100 putative mycorrhizal species and (2) a belowground molecular approach was used to generate DNA sequences of the internal transcribed spacer region from ectomycorrhizae. Unexpectedly, chestnut did not appear to be the dominant underground ectomycorrhizal-forming plant species. This study highlights the need to identify the plant host species when conducting belowground molecular-based surveys and provides preliminary identification of ectomycorrhizal fungi associated with a disjunct stand of American chestnut. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

板栗丰产密度试验

板栗丰产密度试验耿国民柳鎏周久亚陈凯（江苏省中国科学院植物研究所,南京２１００１４）ＯｎｈｉｇｈｙｉｅｌｄｐｌａｎｔｉｎｇｄｅｎｓｉｔｙｉｎｖｅｓｔｉｇａｔｉｏｎｏｆＣｈｉｎｅｓｅｃｈｅｓｔｎｕｔＧｅｎｇＧｕｏＭｉｎｇ,ＬｉｕＬｉｕ,Ｚｈｏｕ...     

Dynamics of twolined chestnut borer Agrilus bilineatus as influenced by defoliation and selection thinning

1 The twolined chestnut borer, Agrilus bilineatus (Coleoptera: Buprestidae), is a major mortality agent of stressed oak trees. However, patterns of abundance and population change are not well understood. 2 We studied the spatial and temporal variation in abundance of twolined chestnut borer adults during a gypsy moth, Lymantria dispar (Lepidoptera: Lymnatriidae), outbreak and examined the influence of both defoliation and thinning on twolined chestnut borer abundance. 3 In stands that were defoliated by gypsy moth, extensive defoliation occurred in one year, and major overstory tree mortality followed in the next. Most mortality occurred in the year preceding the peak year of twolined chestnut borer abundance and abundance of twolined chestnut borer was positively associated with defoliation and mortality in the previous year. 4 Twolined chestnut borers were more frequently associated with poor or fair crown condition trees than trees with good crown condition and were more abundant on members of the red oak group than the white oak group.     

Chinese chestnut production in the United States: Practice,problems, and possible solutions

There are fewer than 162 ha of commercial Chinese chestnut orchards in the United States, with approximately half of these in the Southeast. Large numbers of Chinese chestnut seedlings are planted annually in the United States for home and game food production; however, knowledge about chestnut propagation, fertilization, pests, harvest, storage and marketing is not adequate. There is little commercial marketing of U.S.-grown Chinese chestnuts through roadside markets and local farmers’ markets as the supply is low and unpredictable. However, we yearly import 4.5 mill kg of European chestnuts to satisfy the U.S. market. Successful chestnut orchards will require vegetatively propagated selections, intensive management, mechanical harvesting, and control of insect and disease pests.     

Direct evidence for linkage of roan and extension loci in Belgian horses

A bay roan Brabant Belgian stallion (ERn/ ern) was bred to eight chestnut American Belgian mares (ern/ ern), producing 57 foals. Thirty foals were bay roan, 25 were chestnut, one was bay, and one was chestnut roan. The recombination rate was 0.035 +/- 0.024, indicating fairly close linkage between the roan (Rn) and extension (E) loci.