Tetraploid Forms Research Articles

Construction of new genomes of columnar apple trees in the Russian research institute of fruit crop breeding

Relevance. The article presents data on the creation of new genotypes of columnar apple trees based on interval crossings of the 2x × 4x type using traditional breeding methods and elements of accelerated assessment of hybrid forms using cytoembryological and molecular genetic methods.Results. Cytological assessment of seedlings obtained from the studied interval crossings of six columnar apple varieties and the selected columnar form 29-35-123 with tetraploid forms 30-47-88 and 25-37-45, which are donors of diploid gametes, showed that seedlings with a triple set of chromosomes prevail and their share is 83.0%. The share of diploids accounts for 17.0%. A comparative assessment of the ploidy of offspring showed that the difference between the yield of triploid seedlings in the offspring of families where different donors of diploid gametes (25-37-45 and 30-47-88) were taken as paternal forms is insignificant. From the tetraploid 30-47-88, 81.7% of triploid offspring were obtained, from 25-37-45 — 91.3%.The data of molecular genetic analysis confirm that in combinations where both parents have the scab immunity gene, the yield of immune seedlings is high (70,7%) and corresponds to the splitting on this basis in a ratio of 3:1. n families where only one of the parents carries the Rvi6 gene in its genotype (Garland × 25-37-45, 29-35-123 × 25-37-45, Moscow necklace × 30-47-88 and Constellation × 25-37-45) immune seedlings were less common (52%). A unique combination of columnarity, the Rvi6 gene and a triple set of chromosomes in one genotype is characteristic of 23.1% of seedlings.

Polyploidy in maize: from evolution to breeding.

Polyploidy played an important role in the evolution of the three most important crops: wheat, maize and rice, each of them providing a unique model for studying allopolyploidy, segmental alloploidy or paleopolyploidy. However, its genetic and evolutionary role is still vague. The undelying mechanisms and consequences of polyploidy remain fundamental objectives in the study of eukaryotes. Maize is one of the underutilized crops at the polyploid level. This species has no stable natural polyploids, the existing ones being artificially obtained. From the experimental polyploid series of maize, only the tetraploid forms (4n = 40) are of interest. They are characterized by some valuable morphological, physiological and biochemical features, superior to the diploid forms from which they originated, but also by some drawbacks such as: reduced fertility, slower development, longer vegetation period, low productivity and adaptedness. Due to these barriers to using tetraploids in field production, maize tetraploids primarily found utility in scientific studies regarding genetic variability, inbreeding, heterosis and gene dosage effect. Since the first mention of a triploid maize plant to present, many scientists and schools, devoted their efforts to capitalize on the use of polyploidy in maize. Despite its common disadvantages as a crop, significant progress in developing tetraploid maize with good agronomic performance was achieved leading to registered tetraploid maize varieties. In this review we summarize and discuss the different aspects of polyploidy in maize, such as evolutionary context, methods of induction, morphology, fertility issue, inheritance patterns, gene expression and potential use.

Characteristics of microsporogenesis in the triploid apple tree and it’s parental form in connection with usage in breeding at the polyploid level

An effective method of creating triploid apple cultivars, which are superior in their characteristics to diploid cultivars, is the crossing of heterochromosomal forms of the type: 2x×4x, 4x×2x. In order to provide a wide range of genetic diversity of riploid hybrids, it is necessary to have a large set of tetraploid donor forms of diploid gametes. A limited set of such forms is a limiting factor for this direction of breeding. And the effectiveness of work on obtaining new valuable apple varieties based on the use of the polyploidy method largely depends on their diversity Therefore, the identification of new apple tetraploids, as well as the study of cytoembryological features of their generative structures, the determination of the quality of the formed gametes necessary for successful breeding and for predicting the results of these works are relevant. Meiosis during microsporogenesis was studied in two tetraploid apple forms. To study meiosis during microsporogenesis, temporary pressed specimen were prepared by the acetohematoxylin method; the propionic-lacmoid method was used to determine the ploidy of hybrid offspring. Microscopic studies were carried out on a Nikon-50i microscope at a magnification of 10 x 105 x 40, 10 x 1.5 x 100. The analysis of the course of meiosis during microsporogenesis in apple tetraploid 34-21-39 [30-47-88(4x)×Krasa Sverdlovska(2x)] and its parent form 30-47-88 [Liberty×13-6-106 (Suvorovetz seedling)] showed that the hybrid 34-21-39 was characterized by the most correct course of meiosis. The largest percentage of deviations and the diversity of morphological types of disorders were detected in the form 30-47-88. Common types of violations were noted. Despite the presence of disorders during meiosis in tetraploid forms, microsporogenesis ended with the formation of visually normal one–dimensional pollen: 89% in the form 34-21-39 and 50% in the form 30-47-88. In combinations of crosses involving the studied forms, a high yield of triploid plants was noted. Consequently, the tetraploid apple forms 34-21-39 and 30-47-88 can be recommended for hybridization for the purpose of mass production of triploid seedlings. The results allow us to conclude that the tetraploid apple forms 34-21-39 and 30-47-88 can be used in breeding as pollinators in heteroploid crosses (2x×4x) to obtain triploid genotypes.

Glandular trichomes as a source of antifungal metabolites in a karyologically characterized population of Argyrochosma flava: Morphology and histochemistry

Argyrochosma, a xeric-adapted fern genus mostly from the New World, includes both farinose and non-farinose species. The yellow farina appears to be a synapomorphy of A. flava. The aims of this research were to study the morphology, location, distribution, and density of glandular trichomes; perform a histochemical analysis of the farina secretion; evaluate the biological activity of farinas against phytopathogenic fungi; and characterize the species genetically by making chromosome counts and building the karyotype of A. flava. Usual methods in plant anatomy and histochemistry were performed. Minimum Inhibitory Concentrations (MICs) and Minimum Fungicidal Concentrations (MFCs) of farina against four phytopathogenic fungi were determined by the broth microdilution technique. Chromosome counts and karyotyping metaphase plates were obtained from fiddleheads. The distribution of glandular trichomes in pinnules changes along the ontogenetic development of the frond. The histochemical study of the trichomes revealed the complex nature of the secreted material, including flavonoids and terpenes along with other metabolites. The farina was active against the four pathogenic fungi evaluated, with MICs between 31.25 and 125 μg/mL showing the highest inhibition for Monilinia fructicola. Botrytis cinerea displayed a MIC value of only one-fold dilutions more than the commercial fungicide Carbendazim. Cytogenetically, the base number proposed for the genus is x = 27, which is derived from aneuploidy of x = 29. The genus has diploid and tetraploid forms. The results obtained support the important role of glandular trichomes and farinous exudate secretion in the protection against phytopathogenic fungi. The obtained chromosome numbers support the taxonomic placement of A. flava.

Papirovka tetraploid is a source for summer triploid apple trees creation

Russian Research Institute of Fruit Crop Breeding (VNIISPK) is the oldest breeding and pomological institution of Russia and one of the main suppliers of new apple cultivars in Central Russia. To date, the Institute has created and included in the State Register 56 apple cultivars of different maturation periods for the conditions of the Middle zone of Russia. In addition, our Institute took part in the creation of a number of cultivars for the North Caucasus. We have numerously drawn attention to the value of apple varieties of folk selection in creating adaptive, competitive cultivars. In this paper we tried to show the role of the tetraploid form of Papirovka of folk selection in the creation of new summer triploid cultivars with more regular fruiting and more marketable fruits. 20 cultivars have been created with the participation of the varieties of folk selection, including six cultivars with the participation of Antonovka Krasnobochka: Zarianka, Orlovsky Pioner, Pamyat Isaeva, Patriot, Svezhest and Slavyanin; five cultivars with the participation of tetraploid Papirovka: Avgusta, Dariona, Maslovskoye, Osipovskoye and Yablochny Spas; five cultivars with the participation of folk variety Antonovka Obyknovennaya widely distributed in the central part of Russia: Zdorovie, Imrus, Morozovskoye, Orlovim and Pamyat Voinu; three cultivars with the participation of Skryzhapel: Bolotovskoye, Vavilovskoye and Nizkorosloye; Ranneye Aloye with the participation of Papirovka (diploid). Of particular interest, in our opinion, are the summer triploid cultivars obtained with the participation of the variety of folk selection Papirovka tetraploid.

Terpenoid VOC profiles and functional characterization of terpene synthases in diploid and tetraploid cytotypes of Chrysanthemum indicum L

Chrysanthemum indicum L. is a valuable medicinal plant with diploid and tetraploid forms that are widely distributed in central and southern China, and it contains abundant volatile organic compounds (VOCs). Despite the discovery of some terpene synthase (TPS) in C. indicum (i.e., CiTPS) in previous studies, many TPSs and their corresponding terpene biosynthesis pathways have yet to be discovered. In the present study, terpenoid VOCs in different tissues from two cytotypes of C. indicum were analyzed. We identified 52 types of terpenoid VOCs and systematically investigated the content and distribution of these compounds in various tissues. The two cytotypes of C. indicum exhibited different volatile terpenoid profiles. The content of monoterpenes and sesquiterpenes in the two cytotypes showed an opposite trend. In addition, four full-length candidate TPSs (named CiTPS5–8) were cloned from Ci-GD4x, and their homologous TPS genes were screened based on the genome data of Ci-HB2x. These eight TPSs displayed various tissue expression patterns and were discovered to produce 22 terpenoids, 5 of which are monoterpenes and 17 are sesquiterpenes. We further proposed corresponding terpene synthesis pathways, which can enable the establishment of an understanding of the volatile terpenoid profiles of C. indicum with different cytotypes. This knowledge may provide a further understanding of germplasm in C. indicum and may be useful for biotechnology applications of Chrysanthemum plants.

SCREENING FOR BIOMORPHOLOGICAL AND CYTOGENETIC FEATURES OF POLEMONIUM CAERULEUM L. AFTER COLCHICINE APPLICATION

Background. Currently, it is quite relevant in breeding to create varieties with high yields of raw materials and the content of biologically active compounds.
 This work aim is to identify promising forms of P. caeruleum L. is for further inclusion in the breeding process based on biomorphological, anatomical, cytogenetic studies and the bioproductivity of colchicine-induced and wild-growing forms in comparison with the Lazur variety.
 Materials and methods. To obtain polyploids in 2018, the seeds of the P. caeruleum L. the Lazur variety were germinated in Petri dishes on filter paper at room temperature. When the roots reached the length of the seed, they were placed in different concentrations of colchicine solution 0.05 %, 0.1 %, 0.2 % and 0.52 % for 12 and 24 hours, then washed in running water for three hours.
 Results. The article for the first time presents data on a comparative study of three forms of Polemonium caeruleum L. in terms of morphological characteristics, microscopy of the leaf epidermis and cytogenetic analysis. It was established that the raw materials productivity of the underground part of the plants tetraploid forms in the C1 generation significantly exceeded the diploid and wild forms of plants by 32 %, as well as the yield of seeds by 22 %. In the C2 generation, the yield of raw materials (rhizomes with roots) in tetraploid plants increases in relation to the control by 56 %, seeds by 34 %. Quantitative determination of the amount of triterpene saponins in terms of β-escin in the plant material of three forms of P. caeruleum L. showed an excess of this indicator in the colchicine form by 24 % in the grass and by 36 % in rhizomes with roots, in the wild-growing form - by 15 % in the aerial part and decrease in the underground part by 9 % in relation to the control. It was found that plants of colchicine and wild forms differ in the presence of larger stomata compared to the control. Based on the pattern of DAPI-bandin and the distribution of 45S rDNA and 5S rDNA genes, a generalized species idiogram of blue cyanosis was constructed, taking into account polymorphic variants of DAPI-bandin patterns and indicating the location of the sites of 45S rDNA and 5S rDNA genes. The cytogenetic stability of the resulting tetraploid form was revealed.
 Conclusion. The article presents comparative studies on morphological characteristics, bioproductivity, microscopy of the leaf epidermis and cytogenetic analysis of the tetraploid form (colchicine) of P. caeruleum L. in comparison with the variety Lazur (diploid form) and the wild form of P. caeruleum L. plants.

Does Inducing Tetraploidy in Vaccinium ovatum Improve Fruit Traits and Plant Architecture?

Vaccinium ovatum (evergreen huckleberry) is an evergreen shrub native to the Pacific Northwest. Evergreen huckleberry is diploid (2n = 2x = 24), but unreduced gametes have been reported that facilitated in interspecific tetraploids. To our knowledge, tetraploid forms of evergreen huckleberry have not previously been evaluated. There is interest in this species as a native, edible, evergreen landscape shrub, but it requires improvement of the fruit and plant qualities for an eventual cultivar release. To obtain variation in plant qualities, we induced polyploidy in a collection of plants in 2013. The purpose of this study was to assess the impacts of polyploidy on the fruit and plant qualities of V. ovatum. This fruit and plant quality study provides a contribution to the scientific knowledge base that is currently lacking for evergreen huckleberries. Plant qualities were determined by measuring plant height and width, obtained in Fall 2017. The fruit volume (mm3) and for soluble solids content (SSC, °Brix) were measured using a digital caliper and a digital refractometer, respectively. Measurements were taken on diploid, mixoploid, and tetraploid (2x, 2x + 4x, 4x) cytotypes, once in 2017, five times over 9 weeks in 2018, and three times over 9 weeks in 2019. Tetraploids had larger fruit than diploids in 2017 (P < 0.0001), suggesting there was a gigas effect from polyploidy in evergreen huckleberries. However, during 2018 and 2019, tetraploid fruit was smaller than that of diploid and mixoploid genotypes. Differences were observed in diploid fruit volume among all years (P < 0.0001) such that 2019 was largest and 2017 was smallest. It is unclear what led to this variation. In tetraploids, SSC was statistically significant among years (P = 0.0002) such that 2017 was highest and 2019 was lowest. Although our preliminary data suggested that induced polyploidy may result in larger fruit, this was not observed in subsequent years, and it does not appear that tetraploids necessarily will have larger or sweeter fruit. However, these tetraploids may facilitate crossing with other species at the tetraploid level as a means for improvement of various traits.

Polyploidization Increases the Lipid Content and Improves the Nutritional Quality of Rice.

Plant polyploidization is frequently associated with changes in nutrient contents. However, the possible contribution of metabolites to this change has not been investigated by characterizing the metabolite contents of diploid and tetraploid forms of rice (Oryza sativa L.). We compared the metabolites of a group of diploid–tetraploid japonica brown rice and a group of diploid–tetraploid indica brown rice based on liquid chromatography–tandem mass spectrometry. In total, 401 metabolites were identified; of these, between the two diploid–tetraploid groups, 180 showed opposite expression trends, but 221 showed the same trends (147 higher abundance vs. 74 lower abundance). Hierarchical cluster analysis of differential metabolites between diploid and tetraploid species showed a clear grouping pattern, in which the expression abundance of lipids, amino acids and derivatives, and phenolic acids increased in tetraploids. Further analysis revealed that the lipids in tetraploid rice increased significantly, especially unsaturated fatty acids and phospholipids. This study provides further basis for understanding the changes in rice nutritional quality following polyploidization and may serve as a new theoretical reference for breeding eutrophic or functional rice varieties via polyploidization.

Breeding-oriented evaluation of the progeny of cv. ‘Papirovka tetraploidnaya’ in the Middle Urals

One of the most promising trends in apple breeding is polyploidy. Triploid cultivars show higher fruiting stability and increased self-fertility. The easiest way to obtain triploids is to cross diploid and tetraploid cultivars among themselves. The main limiting factor in this case is a restricted number of initial tetraploid forms whose characteristics affect the quality and prospects of the resulting hybrid progeny.The staff of Sverdlovsk Horticultural Breeding Station in the Middle Urals produced and analyzed 5 hybrid families using cv. ‘Papirovka tetraploidnaya’ as the paternal source; the latter’s pollen was supplied by Acad. E. N. Sedov from the All-Russian Research Institute of Fruit Crop Breeding. Ninety hybrid seedlings were studied.The study showed that ‘Papirovka tetraploidnaya’ with a high degree of probability conveyed the following traits to its progeny: large fruit size, fruit ripening in early summer, midsummer and autumn, loose or medium density of coarse fruit flesh, and nonoutstanding fruit taste (scoring 3.8–4.2 points).

Newly discovered tetraploid Fagopyrum homotropicum in Tibet, China

A cryptic species of Fagopyrum (Polygonaceae), F. homotropicum, is described and illustrated from Mangkang county, Tibet, China. F. homotropicum was firstly discovered in the 90’s, being to be diploid and characterized being a self-pollinating taxon. Detailed information of F. homotropiucm was rarely reported. In this paper, we summarized the morphological and karyological characters of tetraploid form F. homotropiucm (2n=4x=32), it is self-pollinating, and morphology indistinguishable in comparison from the diploid form.

Prospects and methods of polyploid selection of new high-yielding miscanthus clones in the natural climatic conditions of Ukraine

Goal. Expanding the breeding trait collection of breeding genotypes of the genus Miscanthus (Anderson) and the genetic basis for new allotriploid clones by transferring components for hybridization of natural wild species Miscanthus sinensis and Miscanthus sacchariflorus to the tetraploid level.
 Methods. Cytological, biotechnological, fluorescent cytphotometry, field, laboratory.
 Results. The efficiency of polyploidisation for induction of new tetraploid forms of miscanthus in liquid nutrient media supplemented with colchicine (0.05% mass) and for stabilization of myxoploid shoots (0.005% mass) for 6 h of cultivation is examined. The period of exposure for Miscanthus sinensis (2x=2x= 38) and Miscanthus sacchariflorus (2x = 2x = 38) varied from 2 hours to 3 days depending on the genetic origin of the material, with transfer to a hormonal environment. The best indicators of tetraploid induction for Miscanthus sinensis were observed for the exposure period of 2 days with polyploidization efficiency (Db%) of 31.25% and 21.42%, and for Miscanthus sacchariflorus 2 and 6 hours with 35.0% and 27.3%, respectively. The technology of transfering rooted shoots into the soil on the Yaltushkiv Eperimental Breeding Farm was improved and the composition of the soil mixture that provided 99% rooting of culture seedlings at a humidity of 60−70% and air temperature of 35−55°С was found.
 Conclusions. New biotechnological tetraploid lines of Miscanthus sinensis (2xn=4x=76) and Miscanthus sacchariflorus (2xn=4x=76) were created in the conditions of liquid nutrient media supplemented with colchicine (0.05 % mass). It is investigated that flowering of new tetraploid clones in the conditions of Ukraine for the second year of vegetation occurs from late September to early October with formation of fertile pollen grains.

Use of factors of photoperiod duration and growth regulators to increase the yield of mixoploid plants in C0 generation in meadow clover (Trifolium pratense L.)

It has been established that the studied mode of cultivation of meadow clover under controlled environmental conditions, with continuous illumination with an intensity of 18-20 thousand lux and a constant temperature of + 25 °C, causes significant morphological changes in meadow clover. Compared with the optimal (control), the proposed growing regime halves the development time of plants and by the same amount reduces the severity of morphological traits, while simultaneously causing apical dominance in 54% of plants. Spraying plants with phytohormone in the form of naphthylacetic acid in all studied concentrations reduced the growing season by 4-8 days and increased pollen fertility by 8-10%. The optimal concentration of naphthylacetic acid (NLA) was revealed to suppress the growth of secondary meristems in meadow clover under the conditions of an experimental plant growing regime. The most significant effect on the manifestation of apical dominance was shown by the use of naphthylacetic acid at a concentration of 0.001%. The combined use of the proposed growing regime and treatment with naphthylacetic acid at a concentration of 0.001% increased the yield of plants with apical dominance from 54.5% to 76%. The developed method has shown high efficiency for the creation of tetraploid forms of meadow clover. When growing clover C0 generation and selection of mixoploid plants, the yield of mixoploids increased 5.4 times, the survival rate of seedlings increased by 21%, the time to obtain one generation and the selection of mixoploids decreased by 58%.

Ploidy, genetic diversity and speciation of the genus Aronia

Speciation in Aronia is complex based on Amplified Fragment Length Polymorphism (AFLP) and ploidy analysis of 132, mostly wild, accessions. There are four species of Aronia and seven taxonomic groups comprised of species by ploidy combinations. A. melanocarpa can be diploid or tetraploid, with diploid forms occurring in New England and tetraploid forms occurring primarily outside of New England. A. arbutifolia was only found as a tetraploid and did not appear to occur throughout parts of New England as is generally accepted. It is likely that numerous misidentifications of A. arbutifolia have occurred historically. Almost all wild A. prunifolia were tetraploid, with the exception of a single triploid plant. Evidence from AFLP analysis and several accessions expressing a continuum of morphological characteristics between those of A. arbutifolia and A. melanocarpa suggest that A. prunifolia is of interspecific hybrid origin. The occurrence of a natural triploid A. prunifolia accession and our ability to easily create triploid A. prunifolia progeny from diploid A. melanocarpa by tetraploid A. arbutifolia crosses supports the hybrid formation of the A. prunifolia species. Hybrid A. prunifolia origin is also supported by the prevalence of A. prunifolia accessions in geographic areas where A. arbutifolia and diploid A. melanocarpa interface. Most likely, tetraploid A. prunifolia found in the wild result from repeated formation of triploid F1 interspecific hybrids and the triploid bridge mechanism. AFLP analysis, along with morphology and phenology, suggest that a new species of black-fruited Aronia (melanocarpaS) exists in the southern part of the A. melanocarpa geographic range. A. melanocarpaS plants are placed on a separate branch of the AFLP dendrogram that is separate from other Aronia species. Several accessions with large, wide leaves, large fruits and non-rhizomatous growth were found to be A. mitschurinii, an intergeneric hybrid between Aronia and Sorbus. All A. mitschurinii accessions were tetraploid.

Diploid and aneuploid sperm in tetraploid ginbuna, Carassius auratus langsdorfii

Ginbuna (Carassius auratus langsdorfii (Teleostei: Cyprinidae)) occur in diploid, triploid, and tetraploid forms in wild populations. Diploid females reproduce bisexually, whereas polyploid (triploid and tetraploid) females reproduce gynogenetically with no contribution from sperm nuclei. However, tetraploid males produce diploid sperm. The mechanism responsible for the differences in egg and sperm ploidy has not been elucidated as tetraploid males are rare in wild populations. Here, we aimed to characterize the types of sperm and elucidate the mechanism of spermatogenesis in ginbuna. In the present study, we artificially produced tetraploid males by crossbreeding triploid ginbuna females with diploid goldfish (Carassius auratusauratus) males via accidental incorporation of sperm nuclei. We then examined spermatogenesis to reveal the process by which reduced diploid sperm are generated from tetraploid germ cells. DNA fingerprinting by random amplified polymorphic DNA (RAPD)-PCR indicated that the tetraploid progeny had a paternally derived genome. For the tetraploid male sperm, there were narrow (N-type) and broad (B-type) flow cytometrical histograms. The N-type were determined to be diploid with a low coefficient of variation (CV) by flow cytometry. The B-type were found to be aneuploid (hypodiploid to hexaploid) with a high CV. The head sizes of B-type sperm were variable, whereas those of the N-type sperm were uniform. Computer-assisted sperm analysis (CASA) revealed that both the haploid and diploid B-type sperm were weakly motile compared with the haploid sperm of goldfish and the diploid N-type sperm of tetraploid males. Bivalents and various multivalents were observed in the meiotic configurations of diploid spermatogenesis. In aneuploid spermatogenesis, most of the chromosomes were unpaired univalents and there were very few bivalents. Our findings provide empirical evidence for two different types of spermatogenesis in tetraploid C. a. langsdorfii males. Meiotic synapses might explain the observed differences in the ploidy status of the two sperm types.

Ecophysiology of Arabidopsis arenosa, a new hyperaccumulator of Cd and Zn

Arabidopsis arenosa is a pseudo-metallophyte, closely related to the model hyperaccumulator of Cd and Zn Arabidopsis halleri. A. arenosa occurs naturally in both diploid (2C) and tetraploid (4C) form, in contrast to A. halleri in which only diploid forms were found. Moreover, A. arenosa similarly to A. halleri often occupies heavy metal (HM) contaminated sites. Nevertheless, knowledge about the ecophysiology of this species is very limited. Therefore, we examined fourteen populations of A. arenosa of different ploidy from Central Europe in situ, focusing on photosynthetic efficiency, pigment content and ability to accumulate selected elements. The presented results indicate that several tetraploid populations exhibit the features of Cd and Zn hyperaccumulation. On the one hand, we noted differences in physiological parameters between the studied populations, on the other, harshness of the environment caused similar physiological response such as high HM pollution. All these features suggest that A. arenosa, especially as a new hyperaccumulator of Cd and Zn and autopolyploidyzation model, may be considered a very interesting research object, particularly when investigating the mechanisms of HMs accumulation and tolerance in plants.

Reproductive compatibility of Sorbocotoneaster with mountain ash species and varieties that are promising for breeding in Siberia

In Russia, in the Republic of Yakutia, there is the only point in the world where natural intergeneric hybridization of species of the genera Sorbus and Cotoneaster is observed, resulting in the formation of a new hybridogenic genus ×Sorbocotoneaster with a rich polymorphism of parental genera traits. For the selection of mountain ash in Siberia, it is promising to involve Sorbocotoneaster genotypes in artificial hybridization as sources of a complex of economically valuable traits, including winter hardiness, short stature, and self-fertility. Artificial hybridization of the tetraploid selective form Sorbocotoneaster with selected forms and varieties of Sorbus sibirica, S. aucuparia, S. sambucifolia and their hybrids allows obtaining viable hybrid offspring in combinations where Sorbocotoneaster is used as a pollen donor.

Morphological markers with a triploid set of chromosomes by breeding of apple tree at the polyploid level

The results many years of research in the conditions of the Altai low mountains are given the assessment of hybrid apple populations from heterploid crosses according to the characteristics: resistance to scab, degree of culture, growth strength, stem thickness, leaf thickness, leaf index, morphometry of the graft and stipules, ploidy. The correlation was established by the studied indications with the triploid set of chromosomes of hybrids from heteroploidy’s crosses. It is shown that the cytological assessment of karyotypes selected for a complex of morphological features is required in a significantly smaller volume, and varieties of siberian selection are capable for partial formation of germ sacs with a diploid set of chromosomes. Morphological markers for apple tree selection at the polyploid level were determined by identifying seedlings in the juvenile stage with a triploid set of chromosomes inside a hybrid population. The application of morphological markers makes it possible to identify from 14 to 100% of seedlings with a triploid set of chromosomes in dependence on the original tetraploid form.

Intermediate Inheritance with Disomic Tendency in Tetraploid Intergeneric Citrus × Poncirus Hybrids Enhances the Efficiency of Citrus Rootstock Breeding

Rootstocks are crucial for the sustainability of the citrus industry worldwide. Diploid intergeneric Citrus × Poncirus hybrids have contributed considerably to citrus rootstock improvement and their tetraploid (doubled-diploid) forms are important resources for the creation of a new generation of tetraploid rootstocks. To optimize the efficiency of tetraploid rootstock breeding strategies, more knowledge is required on inheritance in the allotetraploid genitors. A set of 159 new SNP markers that fully distinguish Poncirus trifoliata (L.) Raf. from Citrus species was developed from polymorphisms mined in GBS data and used to establish a genetic map of tetraploid citrumelo (C. × paradisi Macfad. × P. trifoliata) and to analyze the meiotic behavior of tetraploid citrumelo and citrandarin (C. reticulata Blanco × P. trifoliata). The tetraploid citrumelo genetic map was highly syntenic and collinear with the clementine reference genome. The apparent intergeneric recombination rate was strongly limited by high preferential chromosome pairing, resulting in intermediate inheritance with disomic tendency. Such inheritance, also observed in tetraploid citrandarin, results in the transmission by the diploid gametes of a high rate of intergeneric heterozygosity. It is therefore expected that a large part of the genetic value selected in the original diploid intergeneric rootstock is transmitted to the tetraploid sexual progenies.

Cytogenetic mechanisms of unisexuality in rock lizards

Darevskia rock lizards is a unique complex taxa, including more than thirty species, seven of which are parthenogenetic. In mixed populations of Darevskia lizards, tri- and tetraploid forms can be found. The most important issues in the theory of reticulate evolution of Darevskia lizards are the origin of parthenogenetic species and their taxonomic position. However, there is little data on how meiosis proceeds in these species. The present work reports the complex results of cytogenetics in a diploid parthenogenetic species – D. unisexualis. Here we detail the meiotic prophase I progression and the specific features оf mitotic chromosomes organization. The stages of meiosis prophase I were investigated by immunocytochemical analysis of preparations obtained from isolated primary oocytes of D. unisexualis in comparison with maternal species D. raddei nairensis. It has been shown that in D. unisexualis at the leptotene-zygotene stages the axial elements and the synaptonemal complex (SC) form typical “bouquets”. At the pachytene-diplotene stage, 18 autosomal SC-bivalents and thickened asynapted sex Z and w univalents were observed. The presence of SYCP1 protein between the lateral elements of autosomal chromosomes proved the formation of assembled SCs. Comparative genomic hybridization (CGH) on the mitotic metaphase chromosomes of D. unisexualis was carried out using the genomic DNA isolated from the parental species D. raddei nairensis and D. valentini. In the pericentromeric regions of half of the mitotic chromosomes of D. unisexualis, specific regions inherited from maternal species have been found. Following our results, we suggest a model for diploid germ cells formation from diploid oocytes without premeiotic duplication of chromosomes in the oogenesis of diploid parthenogenetic lizards D. unisexualis. Taken as a whole, our findings confirm the hybrid nature of D. unisexualis and shed light on heterozygosity and automixis in diploid parthenogenetic forms.