Curly Birch Research Articles

Dissection of figured wood trait in curly birch (Betula pendula Roth var. carelica (Mercklin) Hämet-Ahti) using high-throughput genotyping

Curly (Karelian) birch is a special variety of Betula pendula Roth distributed in the northwestern part of Europe. Karelian birch is well-known for its valuable figured curly wood also known as “wooden marble”. The genetic basis underlying curly wood formation has been debated since last century, however, there was no data about loci responsible for the curly wood trait. In the present study, we analyzed two full-sibs populations derived from experimental crosses of curly birches and segregating for the trait. RADseq genotyping was applied to reveal how many loci are involved in ‘curliness’ formation and to search for genetic variants associated with this trait. One single interval on chromosome 10 was detected containing possible candidate genes. InDel marker BpCW1 was suggested for the first time for marker-assisted selection of trees with curly wood at their earliest stages of development.

Botanical Reserves of Curly Birch in the Republic of Karelia

Botanical Reserves of Curly Birch in the Republic of Karelia

Genus <i>Betula</i> L.: Species-Specific Population-Genetic Features and Taxonomy Problems

The article summarizes and systematizes the results of studies by Russian and foreign authors related to the population-genetic features of the main members (silver birch Betula pendula Roth, downy birch Betula pubescens Ehrh, curly (or Karelian) birch Betula pendula Roth var. carelica (Mercklin) Hämet-Ahti) of the birch genus (Betula L.) growing in the forest zone of Europe. Information is provided about forming of birch populations in the region and about its migration pathways when recolonizing the territory after the Ice Age. We demonstrate that due to certain geographic and climatic affiliations there appeared zones of hybridization between different birch species, which had an effect on the subsequent evolution of this genus. Attention is given to the role of hybridization in shaping the genetic structure of the birch population in the north-western part of continental Europe, where introgression has generated unusual genotypes and haplotypes, among which curly birch has probably become differentiated. We argue that the introgressive hybridization of species observed now and then in the birch genus may be of the main reasons for the problems with definite taxonomic identification of silver birch and downy birch. It is also remarked that curly birch, although meeting the conventional biological criteria of a species, is still regarded a variety of silver birch. Having analyzed the population-genetic features of members of the genus Betula L., the authors conclude that the species status of silver birch and downy birch should be retained in spite of the identification difficulties and that instating curly birch as a separate biological species is advisable. We emphasize the importance and relevance of studying the population-genetic features of both common and rare members of the Betula genus to enable the development of efficient methods and practices of their selective breeding and reproduction of the most valuable genotypes as a solid scientific foundation for sustainable forest management.

Сибсовое потомство карельской березы на Заонежской лесосеменной плантации

The article reports the results of studies on the growth and development of curly birch sibs progeny (produced through controlled pollination) aged 35 and 15 years growing in the Zaonezhye forest seed orchard (sites 1 and 2, respectively) in south-eastern Karelia, Medvezhyegorsky District. The number of trees with signs of wood figure in the seed progeny of curly birch in site 1 was 67 % by the age of 20 years, and by the age of 35 years – almost 80 %. This can probably be attributed to the genetic characteristics of the parent (plus) trees on one hand and to the favorable conditions in the forest seed orchard during the first years of the sibs progeny development on the other. Four of the 36 hybrid families (selected to include forward- and backcrossing products) were used for the case study of the growth and development patterns in stands of different age. The sibs progeny of these hybrid families was dominated by high-stemmed plants, but the main trunk shape in the 15-year-old stand was one with necks and muffs, while in the 35-year-old stand – with small protuberances. The rate of height growth in the trees decreased notably with age, whereas radial (stem diameter) growth, on the contrary, accelerated. As the bark grew thicker, however, the formerly bulgy surface “smoothed down”. We have also identified specific features of the ground vegetation formed under the effect of curly birch plantations of different age (15- and 35 years old). A conclusion drawn from the study is that good results from targeted cultivation of curly birch with figured grain (e.g., for sliced veneer) can be achieved already by the age of 20–35 years. Furthermore, considering the number of trees and their origin, this forest seed orchard constitutes an essential part of the valuable gene pool of curly birch, which may turn into a source for expanded reproduction of the resources of this unique member of the European forest tree flora. For citation: Vetchinnikova L.V., Titov A.F., Kostina E.E., Zhigunov A.V. Sibs Progeny of Curly Birch at the Zaonezhye Forest Seed Orchard. Lesnoy Zhurnal = Russian Forestry Journal, 2023, no. 5, pp. 9–26. (In Russ.). https://doi.org/10.37482/0536-1036-2023-5-9-26

Curly Birch: Some Secrets Remain

The article briefly recapitulates on and systematizes major results of the studies of curly (or Karelian) birch Betula pendula Roth var. carelica (Mercklin) Hämet-Ahti, mainly from the past two or three decades. Its main biological characteristics are described. Facts regarding curly birch resources are provided; the important role of protected areas in conserving its gene pool is emphasized. Good experience of its introduction and re-introduction is demonstrated. The origin of curly birch, the process of figured grain formation in its wood and the question of its taxonomic status are touched upon. It is pointed out that our knowledge of the nature and characteristics of curly birch as a biological object has advanced substantially over the past two or three decades, but two essential questions remain unresolved: a) origin of the curly birch and b) causes and mechanisms of figured grain formation in its wood. Answers to these questions are of much interest both theoretically and for practical causes as they would help preserve the gene pool of curly birch and contribute to augmented reproduction of its resources.

CURLY BIRCH: SOME RESEARCH TAKEAWAYS AND PROSPECTS

The article describes the most important and interesting curly birch research results obtained by staff of the Forest Research Institute KarRC RAS over the institute’s more than half-century history. Quantitative indicators of the dynamics of major publications (monographs, articles in Russian and foreign journals, articles in collected volumes, textbooks) and of intellectual property (patents, know-how, databases) produced by scientists working at the Institute are reported. Their analysis shows that interest in this unique member of the forest flora is great and unfailing, as evidenced by the growing number of recent publications. We emphasize that long-term studies in the field and in the laboratory have produced extensive scientific material, substantially enriching our knowledge of the traits and properties of curly birch, its distinctive features. We indicate the research areas of applied as well as theoretical nature where one can potentially expect to obtain the most interesting results providing a deeper insight into the biological nature of curly birch and which, as the authors believe, will very soon help discover adequate approaches to preservation of the plant’s gene pool and to its extended reproduction in the long run.

Реинтродукция карельской березы

The paper offers a systematic overview of the results of research regarding reintroduction of curly (Karelian) birch Betula pendula Roth var. carelica (Mercklin) Hämet-Ahti published by Russian and foreign authors over the past few decades. We briefly outline the current situation with its resources and the key causes of their decline in the late 20th – early 21st centuries, such as mass-scope illegal logging, vanishing or substantial alteration of typical curly birch habitats, as well as some biological features (fragmented distribution, low competitive capacity, etc.). The main outcomes of the curly birch introduction activities in the areas lying far beyond its natural distribution (mainly to the south-east from it) are reported. It is shown that the experience of curly birch reintroduction in Russia is mostly based on planting of forests and establishment of specially protected areas. The results of curly birch reintroduction in Finland, Sweden, Norway, Germany, Belarus and other countries are observed. Although reintroduction is not equally effective in all countries (its success depends on many factors), it has made and is making a significant contribution to the preservation and augmentation of the resources of this unique member of the European forest tree flora. Importantly, the curly birch from the reintroductions performed in different years and different edaphic and climatic conditions steadily retains its key biological features, such as figured grain and diversity of growth forms and trunk surface characteristics, which once again confirms the authors’ previously expressed opinion that there are grounds for classifying the curly birch as a separate biological species. Proceeding from the analysis of the data amassed by now, it is suggested that that the efficiency of curly birch reintroduction to its natural habitats can be promoted by mainly using the stocking material of local provenance (when restoring populations) or by transferring it from other populations (for repatriation cases). An important role in the preservation and reproduction of curly birch belongs to the micropropagation technique.

SPATIAL AND AGE STRUCTURE OF SILVER BIRCH AND CURLY BIRCH POPULATIONS

The results of an analysis of the spatial and age structure of the common birch in Eurasia – silver birch Betula pendula Roth and a unique representative of the European forest dendroflora – curly birch Betula pendula Roth var. carelic a (Mercklin) Hämet-Ahti and populations are reported, exhibiting significant differences between the plants. Numerous facts and observations (areas, spatial distribution, planting density, ecological niches, competitiveness, life forms, age groups, life expectancy) were analyzed, which showed significant differences between them. The authors believe that this, alongside other biological characteristics, is weighty evidence that curly birch is genetically determined separate from silver birch, and supports the earlier conclusion that curly birch qualifies as an independent species.

Structure and Phylogeny of the Curly Birch Chloroplast Genome.

Curly birch [Betula pendula var. carelica (Merckl.) Hämet-Ahti] is a relatively rare variety of silver birch (B. pendula Roth) that occurs mainly in Northern Europe and northwest part of Russia (Karelia). It is famous for the beautiful decorative texture of wood. Abnormal xylogenesis underlying this trait is heritable, but its genetic mechanism has not yet been fully understood. The high number of potentially informative genetic markers can be identified through sequencing nuclear and organelle genomes. Here, the de novo assembly, complete nucleotide sequence, and annotation of the chloroplast genome (plastome) of curly birch are presented for the first time. The complete plastome length is 160,523 bp. It contains 82 genes encoding structural and enzymatic proteins, 37 transfer RNAs (tRNAs), and eight ribosomal RNAs (rRNAs). The chloroplast DNA (cpDNA) is AT-rich containing 31.5% of A and 32.5% of T nucleotides. The GC-rich regions represent inverted repeats IR1 and IR2 containing genes of rRNAs (5S, 4.5S, 23S, and 16S) and tRNAs (trnV, trnI, and trnA). A high content of GC was found in rRNA (55.2%) and tRNA (53.2%) genes, but only 37.0% in protein-coding genes. In total, 384 microsatellite or simple sequence repeat (SSR) loci were found, mostly with mononucleotide motifs (92% of all loci) and predominantly A or T motifs (94% of all mononucleotide motifs). Comparative analysis of cpDNA in different plant species revealed high structural and functional conservatism in organization of the angiosperm plastomes, while the level of differences depends on the phylogenetic relationship. The structural and functional organization of plastome in curly birch was similar to cpDNA in other species of woody plants. Finally, the identified cpDNA sequence variation will allow to develop useful genetic markers.

Differences in survival and phenotypic traits of curly birch preserved by heterovegetative propagation: a\xa0case study from Central-East Europe

Curly birch (Betula pendula Roth. var. carelica [Merklin] Hämet-Ahti) is a disappearing representative of the Betula genus facing a regeneration failure in a large part of its natural distribution in Europe. The unique long-term study of clonal replications originating in heterogeneous environments enabled the evaluation of long-term survival and phenotypic stability of progenies in seed orchard to assess the conservation and commercial potential of heterovegetative propagation. Seventy-eight geographic sources (95 clone origins) representing the south distribution edge in East-Central Europe were analysed for species variation in survival, growth form, bark colour, and stem quality of parent trees and their vegetative progeny, and the effects of four parental site origin characteristics. The survival rate was 73% after 28–33 years of growth. Retention of curly-grained wood was high, the curly-grained wood structure is heritable and thus clonally efficiently achievable (only 3.5% of grafted individuals showed no occurrence of figured wood structure). The phenotypic expression of curliness manifested on the trunks as bulges, stem growth forms (tree/shrub) and stem technical quality showed a lower degree of stability (coincidence) between the parent trees and heterovegatively propagated progenies. Despite this, the conservation potential of seed orchard is very high, especially when stabilization of the stem growth forms affecting the survival and commercial value of progenies can be probably achieved by a more careful selection of scions. Overall, heterovegetative orchards seem to be a very promising method for the long-term conservation of curly birch populations, which, in addition to their great biological and ecological value, have considerable commercial potential.

A Study of the Genetic Diversity and Differentiation of Northern and Southern Curly Birch Populations

The genetic diversity of northern (in the Republic of Karelia and Finland) and southern (in Belarus) populations of curly birch Betula pendula Roth var. carelica (Mercklin) Hamet-Ahti was compared using microsatellite analysis. As a result, their common features as well as some genetic peculiarities were revealed. We found that the curly birch populations had a fairly high allelic diversity simultaneously with observed heterozygosity not as high as expected, indicating that the accumulation of homozygotes prevailed in the populations, thus increasing the risk of their degradation, especially for northern populations, which have already declined sharply in the past few decades. In the southern population, the allelic diversity turned out to be somewhat higher than in northern ones, possibly due to a larger size and slight fragmentation. Cluster analysis confirmed the separation of the southern population from its northern counterparts, which to some degree corresponds to the well-known “isolation by distance” phenomenon.

Assessment of curly birch introduction prospects

We introduce an analysis of the experience of curly birch introductions accumulated in Russia and abroad, from which the main means and methods of evaluating introduction prospects were derived. It follows from this analysis that the most important and commonly used approaches and criteria are: comparison of the edaphic and climatic conditions in the prospective introduction site and the location from which the source material is taken (climate analogues method), assessment of the origin and biological characteristics of the source material, assessment of the composition of stand-forming tree species and their companion species in the prospective introduction site. In addition, we suggest the “distance method”, providing information about the distance from the species range boundary to the prospective introduction site, and about the distance over which curly birch has been moved for introduction before relative to the “averaged” distance. The importance of cultural operations, stocking rate and density of the planted trees for the expression of “figured grain” and “figure intensity” features in wood is highlighted. It is concluded that although curly birch has quite high ecological plasticity and, accordingly, a high introduction potential, the prospects for its introduction should be assessed using a widest possible set of indirect criteria and indicators, which will collectively yield a more probable future estimate of the introduction outcome, and generate a premise for improving its efficiency. The lack of the said integrated approach to evaluating the prospects of introduction is a key reason for its underperformance, notably reducing the chances of successfully dealing with the tasks of gene pool preservation and augmented reproduction of this unique member of the forest tree flora by means of introductions

О границах ареала карельской березы

The article reports on the application of the best known principles for mapping natural populations of curly (Karelian) birch Betula pendula Roth var. carelica (Mercklin) Hämet-Ahti – one of the most appealing representatives of the forest tree flora. Relying on the synthesis and analysis of the published data amassed over nearly 100 years and the data from own full-scale studies done in the past few decades almost throughout the area where curly birch has grown naturally, it is concluded that its range outlined in the middle of the 20th century and since then hardly revised is outdated. The key factors and reasons necessitating its revision are specified. Herewith it is suggested that the range is delineated using the population approach, and the key element will be the critical population size below which the population is no longer viable in the long term. This approach implies that the boundaries of the taxon range depend on the boundaries of local populations (rather than the locations of individual trees or small clumps of trees), the size of which should not be lower than the critical value, which is supposed to be around 100–500 trees for curly birch. A schematic map of the curly birch range delineated using this approach is provided. We specially address the problem of determining the minimum population size to secure genetic diversity maintenance. The advantages of the population approach to delineating the distribution range of curly birch with regard to its biological features are highlighted. The authors argue that it enables a more accurate delineation of the range; shows the natural evolutionary history of the taxon (although it is not yet officially recognized as a species) and its range; can be relatively easily updated (e.g. depending on the scope of reintroduction); should be taken into account when working on the strategy of conservation and other actions designed to maintain and regenerate this unique representative of the forest tree flora.

Карельская береза: разновидность или самостоятельный вид?

Curly (Karelian) birch is a unique and highly valuable representative of woody flora, whose natural growth has been preserved only in the north-west of continental Europe. The article recapitulates the development of views on the taxonomic status and systematic position of the birch. We have analyzed the numerous facts and observations, which, from our perspective, bear record to correspondence of curly birch to the species taxonomic rank. It was done based on our own and published data, and in accordance with generally accepted criteria of the species (morphological, biochemical, genetic, reproductive, geographical, and ecological). The issues of separateness and relatedness of the birch to other representatives of the genus Betula L. are considered. It is emphasized that the recognition of curly birch as a separate biological species is important not only for scientific reasons, but also has great environmental significance since international and national nature protection documents, regulations and laws are focused on animals and plants with a species status. For citation: Vetchinnikova L. V., Titov A. F. Curly Birch: A Variety or a Separate Species? Lesnoy Zhurnal [Russian Forestry Journal], 2020, no. 1, pp. 26–48. DOI: 10.37482/0536-1036-2020-1-26-48 Funding: The study was carried out within the framework of the state assignment of the Karelian Research Centre of the Russian Academy of Sciences (Forest Research Institute, Institute of Biology, and Department of Multidisciplinary Scientific Research) and covered by the federal budget.

Analysis of structural and functional organization of the curly birch chloroplast genome based on the next-generation sequencing data

The sequencing and annotation of the curly birch chloroplast genome were carried out. A high level of similarity of the structural and functional organization of cpDNA among the species of the Betulaceae family was revealed. A set of primers was developed to assess the level of expression of EST markers of the curly birch cpDNA by the real time PCR method.

The role of protected areas in the conservation of the Curly Birch gene pool

The article is devoted to the problem of conservation of the curly (Karelian) birch and the role of protected areas (PAs) in this effort. Data on curly birch numbers and distribution across PAs of various categories in the Republic of Karelia are reported. In view of its limited resources, curly birch has been recognized as a specially protected variety since the very beginning of its systematic studies (early 1930’s). The history of establishment of the network of PAs featuring curly birch is briefly described, and their current state is assessed. It is shown that in spite of the lack of actual control and tending in the PAs, on the whole they have secured the preservation of more than 90 % of the regionally red-listed curly birch resources. All natural curly birch populations are concentrated within four botanical reserves (“Anisimovschina”, “Spasogubsky”, “Kakorovsky” and “Karelian birch near the village of Tsarevichi”), which collectively occupy no more than 0.01 % of the total area of protected areas. The main reasons for the sharp reduction of curly birch resources, as well as the negative consequences associated with its decline are discussed. Using microsatellite markers, it was shown that a decrease in the total and effective population of the curly birch caused by its prolonged exploitation (including illegal logging) has led to a change in its genetic structure and increased inbreeding. The observed processes have resulted in a decline of the genetic diversity and depletion of the gene pool of the curly birch, as well as a nearly total absence of its viable undergrowth. Nevertheless, PAs established in Karelia have played and continue to play an important role in preserving the gene pool of the curly birch, and its elite trees remain the main target for various scientific studies and practical work for the reproduction and re-introduction of the curly birch.

The origin of the Karelian birch: An ecogenetic hypothesis

The earlier proposed ecogenetic hypothesis on the origin of the curly (Karelian) birch is further developed and detailed based on the published data and our own data. This hypothesis is based on the concept of the interaction of specific natural climatic factors and the conditions that had been established in the northwest of continental Europe during the so-called Little Ice Age with a high population genetic polymorphism and adaptive character of many anatomical and morphological traits and specific physiological and biochemical features of the Betula L. species growing in this area. Various facts and observations favoring the ecogenetic hypothesis of the origin of the Karelian birch are described.

Simple inheritance of a complex trait: figured wood in curly birch is caused by one semi-dominant and lethal Mendelian factor?

Even though individuals with a deviant morphology have been elemental in genetics of model species, they have thus far been largely ignored in the studies of forest trees. Here we studied the inheritance of curly-grained and brown-figured wood phenotype in curly birch (Betula pendula var. carelica (Mercklin) Hämet-Ahti). In addition of the figured wood, curly birches display reduced and aberrant growth, indicating that the causative locus (loci) is (are) vital for normal tree development. To explore the genetic basis of this mutation, we studied the inheritance of the curly birch phenotype in a progeny trial (crosses between curly birch parent trees, between curly and normal phenotypes, and from selfings of curly trees). Based on the external morphology, the phenotypes of 11-year-old progeny trees were scored as either curly or wild. Based on the phenotypic segregation ratios, we postulate a simple Mendelian inheritance model for curliness: (i) a one-locus, two-allele model in which the allele coding for curly phenotype is dominant over the allele coding for normal phenotype and (ii) the semi-dominant curly allele is lethal when homozygous. We expect that further studies on the molecular genetic basis of the curly birch phenotype will provide valuable information on the developmental pathways involved in wood formation.

Evaluation of a New Temporary Immersion Bioreactor System for Micropropagation of Cultivars of Eucalyptus, Birch and Fir

The use of liquid instead of solid culture medium for the micropropagation of plants offers advantages such as better access to medium components and scalability through possible automation of the processes. The objective of this work was to compare a new temporary immersion bioreactor (TIB) to solid medium culture for the micropropagation of a selection of tree species micropropagated for commercial use: Nordmann fir (Abies nordmanniana (Steven) Spach), Eucalyptus (E. grandis x E. urophylla), Downy birch (Betula pubescens Ehrh), and Curly birch (Betula pendula var. carelica). Cultivation of explants in the TIB resulted in a significant increase of multiplication rate and fresh weight of Eucalyptus and B. pendula, but not Betula pubescens. In addition, the fresh weight of embryogenic tissue and the maturation frequency of somatic embryos increased significantly when an embryogenic cell line of A. nordmanniana was cultivated in the TIB compared to solid culture medium. These results demonstrate the potential for scaling up and automating micropropagation by shoot multiplication and somatic embryogenesis in commercial tree species using a temporary immersion bioreactor.

Structural and functional peculiarities of plants from the genus Betula L. at early stages of ontogenesis

The morphological, biochemical, and physiological characteristics of silver birch (Betula pendula Roth), curly birch (B. pendula Roth var. carelica), and downy birch (B. pubescens Ehrh.) at early stages of ontogenesis in natural conditions were investigated. Some intra- and interspecific peculiarities of the morphophysiological properties were determined. Priority development of the underground mass for the seedlings of curly birch and that of the aboveground mass for the seedlings of silver birch and downy birch were found. The leaf of curly birch is developed more actively as compared with those in the other two species under equal potential possibility of the growth of their leaves by elongation. A high similarity of the mineral composition (C, N, P, K) of different forms and species of birches was demonstrated. For silver birch the maximum values of the stomatal conductance, rate of photosynthesis, and transpiration under similar atmospheric and soil conditions were obtained. In downy birch we found a higher efficiency of water use. The highest values of the maximum rate of ribulose 1,5-bisphosphate carboxylase/oxygenase carboxylation were found in curly birch. This may serve as an indicator of its shade tolerance, as compared with silver birch and downy birch.