Genus Castanea Research Articles

The Disease Triangle of Chestnut: A review of host, pathogen, and environmental interactions of chestnuts cultivated in the eastern United States

Chestnuts, the edible seeds of the genus Castanea, are a perennial food crop closely tied to the global migration of humans throughout history and have recently been gaining popularity in agriculture and forest restoration in eastern North America. Cultivation of chestnuts yields nutritionally balanced food while fostering economic development, food security, and environmental health. However, diseases and insect pests threaten successful ecological restoration and food production. In this review we explore conditions affecting chestnuts in the eastern United States through the lens of the disease triangle. A “host” in the disease triangle is not merely a single tree, but a tree including its constituent population of fungal endophytes. Chestnut trees are rich with microbial life, and the sustainability of chestnuts in forest and cultivated settings may lie in understanding and manipulating microbial communities to improve plant health and control destructive diseases. To benefit from the ecological and economic potential of chestnuts on the landscape, it may be necessary to select locally adapted chestnut trees, regardless of pedigree, that are resilient against cosmopolitan pathogens. With transport of plants and pathogens throughout the globe, and with landscape level environmental changes over the last century, chestnut trees in the eastern United States (U.S.) are in a unique disease landscape compared to their ancestors. Diseases of economic concern from fungi and fungal-like organisms include chestnut blight (Cryphonectria parasitica) and ink disease (Phytophthora cinnamomi) on American and European chestnuts, oak wilt (Bretziella fagacearum) on all chestnut species, and the emerging diseases of brown rot (Gnomoniopsis smithogilvyi) and chestnut anthracnose (Colletotrichum henanense). The eastern U.S. has experienced profound environmental changes over the 20th century and into the early 21st century. These changes happen to coincide with the demise of the American chestnut in the eastern forest, efforts to re-establish chestnut as a forest species, and the rise in cultivation of multiple chestnut species and hybrids as a culinary crop. Chestnut trees growing in the early 21st century face different environmental circumstances than the American chestnuts of pre-colonial times, including changes in forest composition, rainfall changes and acidification, industrialized agriculture’s increased chemical inputs, rising global temperatures, and increased levels of carbon dioxide in the atmosphere. We conclude that chestnut tree species for both forestry and agriculture should be considered based on current fitness, adaptability, and economic and ecological value considering continued dynamics in host and pathogens distributions and anthropogenically driven climatic and edaphic conditions.

New insights into the evolution and local adaptation of the genus Castanea in east Asia.

Chestnut plants (Castanea) are important nut fruit trees worldwide. However, little is known regarding the genetic relationship and evolutionary history of different species within the genus. How modern chestnut plants have developed local adaptation to various climates remains a mystery. The genomic data showed that Castanea henryi first diverged in the Oligocene ~31.56 million years ago, followed by Castanea mollissima, and the divergence between Castanea seguinii and Castanea crenata occurred in the mid-Miocene. Over the last 5 million years, the population of chestnut plants has continued to decline. A combination of selective sweep and environmental association studies was applied to investigate the genomic basis of chestnut adaptation to different climates. Twenty-two candidate genes were associated with temperature and precipitation. We also revealed the molecular mechanism by which CmTOE1 interacts with CmZFP8 and CmGIS3 to promote the formation of non-glandular trichomes for adaptation to low temperature and high altitudes. We found a significant expansion of CER1 genes in Chinese chestnut (C. mollissima) and verified the CmERF48 regulation of CmCER1.6 adaptation to drought environments. These results shed light on the East Asian chestnut plants as a monophyletic group that had completed interspecific differentiation in the Miocene, and provided candidate genes for future studies on adaptation to climate change in nut trees.

The Neogene-Quaternary palynological record of Castanea in the American southeast

The genus Castanea, divided into seven extant species of trees worldwide, includes the American chestnut, C. dentata. This once common North American tree has been nearly eliminated from the landscape due to the appearance of chestnut blight early in the Twentieth Century. Castanea has a long history as a component of palynological assemblages, though megafossil paleobotanical remains are quite rare. The distributions of what are believed to be Castanea pollen as they have been derived from coastal plain and near-shore sediments dating back to the Neogene of the coastal plain of the southeastern US are discussed. The abundances of Castanea pollen in microfossil preparations are carefully considered relative to the concept of ‘pollen sum’ and while it appears that the trees were quite abundant as components of coastal woodlands during the Neogene, the actual number of pollen we found in samples is quite low. American chestnut trees continued to be important into the late Pleistocene and through the time when humans first occupied both coastal and inland areas of the southeastern US.

Textile Physical Barriers against the Chestnut Gall Wasp Dryocosmus kuriphilus

Dryocosmus kuriphilus Yasumatsu is a species originating from China that, during the 20th century, has spread rapidly throughout many countries, affecting mainly different species of the genus Castanea spp. In fact, it is considered to be the most important pest of chestnut trees (Castanea sativa Miller), causing significant production losses. The adoption of complementary measures to chemical and biological controls would contribute to the control of the pest. In this sense, the use of textile physical barriers could prevent the rapid spread of this species among the production centers. Therefore, the objective of this study is to define the characteristics of a textile that protects young plants that have been produced in nurseries. For this purpose, some commercial textiles have been selected based on the morphometric characterization of the species and these textiles have been accurately measured in order to compare their dimensions with those of the insects. Finally, tests have been carried out in order to measure the efficacy of the textiles under laboratory conditions, controlling the air velocity and the temperature. The results reveal that, in general, theoretical efficacy may not be a good predictor of practical results. A fully effective screen has been found against this species and its design characteristics can be used as a starting point for new, more optimized designs.

Genome-Wide Sequence-Based Genotyping Supports a Nonhybrid Origin of Castanea alabamensis

Abstract— The genus Castanea in North America contains several tree and shrub taxa of conservation concern. The two species within the group, American chestnut (Castanea dentata) and chinquapin (C. pumila sensu lato), display remarkable morphological diversity across their distributions in the eastern United States and southern Ontario. Previous investigators have hypothesized that hybridization between C. dentata and C. pumila has played an important role in generating morphological variation in wild populations. A putative hybrid taxon, Castanea alabamensis, was identified in northern Alabama in the early 20th century; however, the question of its hybridity has been unresolved. We tested the hypothesized hybrid origin of C. alabamensis using genome-wide sequence-based genotyping of C. alabamensis, all currently recognized North American Castanea taxa, and two Asian Castanea species at > 100,000 single-nucleotide polymorphism (SNP) loci. With these data, we generated a high-resolution phylogeny, tested for admixture among taxa, and analyzed population genetic structure of the study taxa. Bayesian clustering and principal components analysis provided no evidence of admixture between C. dentata and C. pumila in C. alabamensis genomes. Phylogenetic analysis of genome-wide SNP data indicated that C. alabamensis forms a distinct group within C. pumila sensu lato. Our results are consistent with the model of a nonhybrid origin for C. alabamensis. Our finding of C. alabamensis as a genetically and morphologically distinct group within the North American chinquapin complex provides further impetus for the study and conservation of the North American Castanea species.

Comparative Analysis of the Complete Chloroplast Genomes of Four Chestnut Species (Castanea)

Chloroplast (cp) DNA genomes are traditional workhorses for studying the evolution of species and reconstructing phylogenetic relationships in plants. Species of the genus Castanea (chestnuts and chinquapins) are valued as a source of nuts and timber wherever they grow, and chestnut species hybrids are common. We compared the cp genomes of C. mollissima, C. seguinii, C. henryi, and C. pumila. These cp genomes ranged from 160,805 bp to 161,010 bp in length, comprising a pair of inverted repeat (IR) regions (25,685 to 25,701 bp) separated by a large single-copy (LSC) region (90,440 to 90,560 bp) and a small single-copy (SSC) region (18,970 to 19,049 bp). Each cp genome encoded the same 113 genes; 82–83 protein-coding genes, 30 transfer RNA genes, and four ribosomal RNA genes. There were 18 duplicated genes in the IRs. Comparative analysis of cp genomes revealed that rpl22 was absent in all analyzed species, and the gene ycf1 has been pseudo-genized in all Chinese chestnuts except C. pumlia. We analyzed the repeats and nucleotide substitutions in these plastomes and detected several highly variable regions. The phylogenetic analyses based on plastomes confirmed the monophyly of Castanea species.

The complete chloroplast genome of Castanea sativa, an endemic to Europe

Sweet chestnut (Castanea sativa) is an endemic species of genus Castanea in Europe, which is widespread in the southern part of continental Europe. The complete genome sequence of chloroplast was determined through Illumina NovaSeq platform. Totally the genome of chloroplast was 160,938 bp in length, GC rich (36.8%), comprising a pair of 25,726 bp inverted repeat sequences, separated by a 90,519 bp large and 18,967 bp small single-copy regions. There were 129 genes, including 37 transfer RNA genes, 8 ribosomal RNA genes, and 84 protein-coding genes. The phylogenetic tree analysis showed that C. sativa exhibited the closest relationship with Castanea henryi.

Fine Morphology of Antennal and Ovipositor Sensory Structures of the Gall Chestnut Wasp, Dryocosmus kuriphilus.

Simple SummaryHymenoptera encompass a large group of insects with different habits, ranging from phytophagy to parasitic/predatory lifestyles. This is also true in the superfamily Cynipoidea, where phytophagy becomes highly specialized towards the exploitation of specific plant tissues (i.e., buds), leading to the induction of galls. In this paper, we investigated the organization of antennal and ovipositor sensory structures in the chestnut gall wasp, Dryocosmus kuriphilus. This insect became a major threat to chestnut production in Italy in the last 15 years. We investigated only females (this is a parthenogenetic species with thelytoky), and on the antennae we found several sensilla with the clear functional specialization to different groups of stimuli, with almost no overlapping among each sensilla. Similarly, specialization was also found on the ovipositor where groups of gustatory and mechanoreceptive sensilla were observed. This information represents an advancement in the knowledge of this pest, which may be useful to understand the biological role of plant derived chemical cues or to implement new control methods.Dryocosmus kuriphilus is a gall-inducing insect, which can cause significant damage on plants of the genus Castanea Mill., 1754. Antennae and ovipositor are the main sensory organs involved in the location of suitable oviposition sites. Antennal sensilla are involved in the host plant location, while ovipositor sensilla assess the suitability of the ovipositional bud. On both organs, diverse sensillar organs are present. Here, the distribution and ultrastructural organization of the sensilla were investigated by scanning and transmission electron microscopy. The antennae of D. kuriphilus are filiform and composed of 14 antennomeres, with the distal flagellomere bearing the highest number of sensilla. On the antennae, 6 sensilla types were found; sensilla chaetica, campaniformia, coeloconica-I, coeloconica-II, trichoidea and placoidea. The sensilla placoidea and trichoidea were the most abundant types. On the external walls of the ovipositor, gustatory and mechanoreceptive sensilla were observed. Internally, the egg channel hosted two additional sensory structures. The putative functional role of each sensilla in the context of insect’s ecology is discussed as well as the ovipositional mechanism used by this insect.

Recent Advances in Adventitious Root Formation in Chestnut.

The genus Castanea includes several tree species that are relevant because of their geographical extension and their multipurpose character, that includes nut and timber production. However, commercial exploitation of the trees is hindered by several factors, particularly by their limited regeneration ability. Regardless of recent advances, there exists a serious limitation for the propagation of elite genotypes of chestnut due to decline of rooting ability as the tree ages. In the present review, we summarize the research developed in this genus during the last three decades concerning the formation of adventitious roots (ARs). Focusing on cuttings and in vitro microshoots, we gather the information available on several species, particularly C. sativa, C. dentata and the hybrid C. sativa × C. crenata, and analyze the influence of several factors on the achievements of the applied protocols, including genotype, auxin treatment, light regime and rooting media. We also pay attention to the acclimation phase, as well as compile the information available about biochemical and molecular related aspects. Furthermore, we considerate promising biotechnological approaches that might enable the improvement of the current protocols.

Castanea spp. Agrobiodiversity Conservation: Genotype Influence on Chemical and Sensorial Traits of Cultivars Grown on the Same Clonal Rootstock.

A large species diversity characterises the wide distribution of chestnuts in Asia, North America, and Europe, hence reflecting not only the adaptation of the genus Castanea to diverse environmental conditions, but also to different management strategies encompassing orchards. The characterisation and description of chestnut populations and cultivars are crucial to develop effective conservation strategies of one of the most important Italian and European fruit and wood species. Chestnut cultivars grown in the same pedoclimatic conditions and on the same clonal rootstock were characterised with sensory, spectrophotometric, and chromatographic analysis to determine the phytochemical composition and nutraceutical properties. A multivariate approach, including principal component analysis and conditional inference tree models, was also performed. The ease of peeling, seed colour, and intensity of sweetness were the sensory descriptors that allowed us to differentiate C. sativa cultivars. Antioxidant capacity ranged from 9.30 ± 0.39 mmol Fe+2 kg−1 DW (‘Bouche de Bètizac’) to 19.96 ± 1.89 mmol Fe+2 kg−1 DW (‘Garrone Rosso’). Monoterpenes represented the main component, reaching 88% for hybrids, followed by polyphenols (10–25% for hybrids and chestnuts, respectively). A multivariate approach showed that phenolic acids and tannins were the bioactive classes with the highest discriminating power among different genotypes, and that genotype is a significant variable (p < 0.05). In addition, most of the analysed chestnut cultivars showed a content of bioactive compounds similar to or higher than the main hazelnut, walnut, and almond varieties. Chestnut agrobiodiversity could be intended as strictly associated to the genotype effect and underlines the large variability within the genus Castanea, and therefore, the importance of in farm and ex situ conservation of local germplasm is part of a global strategy aimed at increasing the levels of agrobiodiversity.

Pollen morphology of chestnut cultivars in southern China by using scanning electron microscope

The morphological characteristics of pollen grains of 16 cultivars belonging to two species of the genus Castanea (Castanea mollissima and C. henryi) collected from southern China were observed by using scanning electron microscope (SEM). The length of polar axis (PL), the equatorial diameter (ED), the length of colpus (CL) of grain, P/E ratio (polar axis to equatorial diameter), P/C ratio (polar axis to colpus length), and C/E ratio (colpus length to equatorial diameter) were measured and their variations were compared among studied taxa. The result of this study indicated that chestnut pollen grain was a tricolporate in aperture type, and aperprolate type in equatorial view. The morphological characteristics were mainly represented by PL, ED and CL as revealed by principal components analysis, which accounted for 99.56% of the total variations. The cluster analysis by the UPGMA tree divided the taxa into three groups and showed a great morphological affinity among the 16 cultivars.

Hot water treatment: an effective method for disinfecting Castanea sativa mill. dormant scions against Dryocosmus kuriphilus Yasumatsu.

The Asian chestnut gall wasp (ACGW) Dryocosmus kuriphilus Yasumatsu is the most severe pest of the genus Castanea worldwide. After its arrival in Europe, the insect dispersed rapidly from Italy to other European countries, as well as spreading over long distances within each country because of the unintentional transport of infested chestnut material owing to the fact that infestation inside the dormant buds is visually undetectable. Hot water treatment (HWT) has been tested in terms of pest and diseases control in propagation processes with a wide range of plant material and species, including the Asian chestnut Castanea mollissima cv 'Qing'. Taking into account the different thermal tolerances of plant species, an experiment to disinfect Castanea sativa scions from ACGW by HWT was performed. The effects of the immersion of dormant scions for 10min at two water temperatures (49 and 52 °C), with and without a previous period of water hydration, were tested. A 10min soak at 49 °C was effective in killing ACGW larvae while retaining an excellent percentage of successful grafts. The pre-HWT hydration stage did not influence the success of the treatment. Positive shoot growth was also recorded after HWT. We report for the first time the effectiveness of a simple and environmentally friendly protocol based on hot water for the disinfection of European chestnut (C. sativa) scions against D. kuriphilus. This will enable nurseries to supply plants free from this pest, preventing the insect dispersion, which will have a positive socio-economic impact to the chestnut tree sector. Also positive environmental impact will be favoured as gall wasp proliferation will decrease. © 2019 Society of Chemical Industry.

5S Ribosomal DNA of Distantly Related Quercus Species: Molecular Organization and Taxonomic Application

The genus Quercus (oak) is a widespread and economically important genus of tree plants. The intrageneric taxonomy of this group remains controversial due to widely distributed interspecific hybridization and convergent similarity of morphological traits. Further progress in this problem requires application of molecular methods. Taking into account that the comparison of 5S rDNA was successfully used in the molecular taxonomy of plants, we cloned and sequenced this genomic region for representatives of three taxo-nomically distant Quercus species: Q. acutissima (sect. Cerris) and Q. glauca (sect. Cyclobalanopsis) from East Asia and Q. texana (sect. Lobatae) from North America. We also identified 5S rDNA in the genome sequences available in the Genbank database for North American species Q. lobata (sect. Quercus) and for the related genus Castanea. It was found that the 5S rDNA repeated units demonstrate a high level of intragenomic sequence similarity in representatives of genus Quercus. The potential external elements of the 5S rDNA promoter differ from those in other families of dicotyledonous plants. The results of the comparative sequence analysis of the 5S rDNA intergenic spacer region support the existing taxonomy of the genus and indicate the isolated position of section Cyclobalanopsis, which can be considered as a separate subgenus.

Identification and pathogenicity of Cryphonectriaceae species associated with chestnut canker in China

Cryphonectriaceae species cause serious canker diseases on chestnut, oak and eucalypt trees. Recently, canker symptoms with typical orange fruiting bodies were observed on Chinese chestnut and oak trees in Hebei, Hubei, Shaanxi and Shandong Provinces in China. In the present study, isolates of these fungi were identified based on phylogenetic and morphological evidence, and their pathogenicities were tested on detached chestnut (Castanea mollissima) branches. DNA sequence comparisons of the internal transcribed spacer (ITS) regions and two regions of β‐tubulin (TUB1/TUB2) indicate that these isolates represent five species in the Cryphonectriaceae, viz. Cryphonectria japonica, Cryphonectria parasitica, Aurantiosacculus castaneae sp. nov., Cryphonectria neoparasitica sp. nov. and Endothia chinensis sp. nov. The sexual morph of Aurantiosacculus is discovered for the first time and can be distinguished from the other genera in Cryphonectriaceae by dark brown ascospores and tubiform appendages at both ends. Cryphonectria neoparasitica sp. nov. is different from the other Cryphonectria species by its aseptate ascospores. Endothia chinensis sp. nov. is the sole species in Endothia infecting the host genus Castanea. Additionally, it is much smaller than E. gyrosa and narrower than E. singularis in ascospores. The inoculation results showed that these five Cryphonectriaceae fungi isolated from chestnut or oak are all pathogenic to tested chestnut branches. Cryphonectria parasitica appears to be the most aggressive fungus, followed by C. neoparasitica sp. nov., C. japonica, E. chinensis sp. nov. and A. castaneae sp. nov.

Evaluation of the descriptive characteristics of chestnut

The chestnut (Castanea spp.) tree is extremely valuable for it ecological role in the environment as well as its role in the production of sweet, edible nuts, decay resistant timber, and the production of chemical compounds such as tannins. Although native to the temperate zone of the northern hemisphere, it has been planted successfully throughout the southern hemisphere including Australia, New Zealand and Chile. Currently, the genus Castanea is represented by 13 species ranging in size from shrubs to large trees. Five species of Castanea are native to East Asia, seven species are native to North America and one species is native to Europe. Many chestnut cultivars have been selected or bred for various purposes such as improving nut or timber quality, increasing yield, enhancing resistance to diseases or pests and winter hardiness. For the purpose of registering new cultivars, distinctness, uniformity and stability (DUS) of the cultivars need to be described and verified. For this aim, morphological characteristics of the cultivar candidates should be determined. There are many morphological traits used for identifying cultivar candidates. However, reliable characteristics need to be selected and scored. Generally, the International Union for the Protection of New Varieties of Plants (UPOV) criteria have been used for this purpose, but we believe the UPOV criteria need to be updated. In this review, various descriptive morphological chestnut parameters are discussed to promote the list of current and new criteria.

Molecular studies conducted in chestnut

Chestnut, genus Castanea in Fagaceae family, usually spreads in different regions of the Northern Hemisphere. It is well-known that 13 species of the genus are important in human nutrition since ancient times. Major distribution areas of these species are China, Korea, Japan, Turkey, Southern Europe and North America. Castanea sativa, which also includes Anatolian chestnut, is a native species of the Mediterranean basin. Although the center of origin is unknown, it has been reported that Castanea sativa was spread from Anatolia and to Europe. According to the latest FAO data, total world chestnut production quantity is 2.261.589 t mainly in China (1.879.031 t), Turkey (64.750 t), Korea (56.244 t) and Italy (50.889 t). Chestnut species take place as an important point in genetic diversity but chestnut production is adversely affected in almost all countries caused primarily by chestnut blight (Cryphonectria parasitica) and root rot (Phytophthora cambivora), so as some other significant threats such as incorrect forestry practices, adversely changing environmental conditions, which recently have increasing importance. These factors still continue to threat the worldwide chestnut cultivation areas and natural population. Therefore, some methodologies have been applied to overcome problems about chestnut cultivation, to conserve genetic variability in situ and ex situ conditions, and to investigate the changes produced by former threats. Some of the conventional methods used in those studies take a long time and they have been complemented by molecular studies with the aim of shortening breeding programs, which include the identification of the responsible genes for nut composition and determination of some chestnut diseases, such as root rot (Phytophthora cambivora), by genetic mapping, but also determining the genetic relationships among genotypes. Molecular studies are also needed for generating gene maps to identify the gene regions that control other significant traits in order to be used in marker-assisted selection. In this study, we present the most recent molecular studies on chestnut in the world.

Pooled whole-genome sequencing of interspecific chestnut (Castanea) hybrids reveals loci associated with differences in caching behavior of fox squirrels (Sciurus niger L.).

Dispersal of seeds by scatter‐hoarding rodents is common among tropical and temperate tree species, including chestnuts in the genus Castanea. Backcrossed (BC) interspecific hybrid chestnuts exhibit wide variation in seed traits: as the parent species (Castanea dentata and C. mollissima) have distinct seed phenotypes and tend to be handled differently by seed dispersers, phenotypic variation in BC trees is likely due to inheritance of genes that have undergone divergent evolution in the parent species. To identify candidate genomic regions for interspecific differences in seed dispersal, we used tagged seeds to measure average dispersal distance for seeds of third‐generation BC chestnuts and sequenced pooled whole genomes of mother trees with contrasting seed dispersal: high caching rate/long distance; low caching rate/short distance; no caching. Candidate regions affecting seed dispersal were identified as loci with more C. mollissima alleles in the high caching rate/ long‐distance pool than expected by chance and observed in the other two pools. Functional annotations of candidate regions included predicted lipid metabolism, dormancy regulation, seed development, and carbohydrate metabolism genes. The results support the hypothesis that perception of seed dormancy is a predominant factor in squirrel caching decisions, and also indicate profitable directions for future work on the evolutionary genomics of trees and coevolved seed dispersers.

Molecular characterization of Fagaceae species using inter-primer binding site (iPBS) markers.

Retrotransposons (RTNs) contribute for genome evolution, influencing its size and structure. We investigated the utility of the RTN-based markers inter-primer binding site (iPBS) for the molecular characterization of 25 Fagaceae species from genera Castanea, Fagus and Quercus. The assessment of genetic diversity, relationships and structure, as well as taxonomic classification of Fagaceae based on molecular data is important for definition of conservation, forestry management strategies and discrimination among natural hybrids and their parents since natural hybridization may increase with the climate changes. Here, iPBS primers designed by other authors were tested alone and combined. Some of them were discriminative, revealed polymorphism within and among taxa allowing the production of a total of 150 iPBS markers. In addition, several monomorphic iPBS markers were also amplified in each taxon. The UPGMA dendrogram based on the pooled iPBS data revealed 27% of genetic similarity among species. The individuals were clustered per genus and most of the oaks per infrageneric group corroborating the adopted taxonomy. Globally, the iPBS markers demonstrated suitability for DNA fingerprinting, determination of phylogenies and taxonomic discrimination in Fagaceae, and could constitute a useful and alternative tool for germplasm characterization, and for definition of conservation strategies and forestry management. Moreover, these markers would be useful for fingerprinting natural hybrids that share morphological similarities with their parents. Since iPBS markers could also enable insights about RTNs evolution, an eventual correlation among iPBS polymorphism, variability of RTN insertions and/or genome size in Fagaceae is discussed.

Impact of the Asian Chestnut Gall Wasp, Dryocosmus kuriphilus (Hymenoptera, Cynipidae), on the Chestnut Component of Honey in the Southern Swiss Alps.

The Asian chestnut gall wasp (ACGW; Dryocosmus kuriphilus Yasumatsu, Hymenoptera, Cynipidae) is considered as one of the most dangerous pests of the genus Castanea. In southern Switzerland, repeated heavy ACGW attacks prevented chestnut trees from vegetating normally for years before the arrival and spread of the biological control agent Torymus sinensis (Kamijo, Hymenoptera, Torymidae). This resulted in a greatly reduced green biomass and flower production. In this paper, we analyze the impact of such an ecosystem alteration of the environment on the composition of produced honey. Six beekeepers were chosen from sites with different densities of chestnut trees, each of which providing series of honey samples from 2010 to 2016. We determined the chestnut component in the honeys via a combined chemical and sensory approach, and correlated the obtained results with the degree of yearly ACGW-induced crown damage and weather conditions during the period in question in the surrounding chestnut stands. The chestnut component in the analyzed honey sample series showed a strong correlation with the degree of ACGW-induced crown damage, whereas meteorological conditions of the corresponding year had a very marginal effect. Decreases in the chestnut component of the honey were statistically significant starting from a ACGW infestation level of 30%.

Application of Biotechnology in the Conservation of the Genus Castanea

Castanea is a hardwood forest genus of considerable agro-economic importance for both timber and nut production. Chestnuts are one of the most significant nut crops in the temperate zone. However, this species is threatened by pollution, social factors, economical changes, and two major fungal diseases: ink disease (Phytophthora spp.), and chestnut blight canker (Cryphonectria parasitica). Similar to other wood species, chestnuts are difficult to propagate both generatively by seed and vegetatively by means of grafting or cuttings. Biotechnological methods such as in vitro culture have been developed in the last few years as an alternative to conventional vegetative propagation. Biotechnology plays a very important role not only in the propagation of selected individuals (being used at a commercial level), but also in its short-term preservation, and offers the possibility of preserving the propagated material in the medium-term (cold storage) or long-term using cryopreservation.