Common walnut (Juglans regia L.) is a valuable nut crop widely distributed within the temperate climate zone. It has several secondary centers of origin associated with refugia formed during the LGM (Last Glacial Maximum) period, one of which was presumably located in the Caucasus region. Currently, walnut populations of the Caucasus are studied fragmentarily, especially in the northeast. Our study is aimed at investigating the genetic diversity, population structure, and possible walnut introduction processes in the Caspian region of the Northeast Caucasus (Dagestan). Genotyping using 11 SSR markers was performed for 158 samples from local walnut populations. Also, to identify the introduction facts, 42 varieties of different geographical origin were added to research. The SSR markers genetic diversity in the analysis of population varied from four to 20 alleles per locus, with an average value of 9.82. Analysis of the genetic structure revealed significant genetic differences between the subpopulations of the Mountain and Flatland Dagestan. Presumably, the structure of the gene pool could have been influenced by terrain factors and ethnocultural characteristics. Subpopulations of Flatland Dagestan have an intermediate position between the western cultivars and the gene pool of Mountain Dagestan, which subpopulations showed significant genetic isolation. In the studied samples set of population selections, the established introduction facts were rare. We have suggested that a significant part of the walnut gene pool from Mountain Dagestan has an autochthonous origin from plants that survived the LGM in the Caucasian refugia. Our results are the basis for further studies of the local gene pool and verification of hypothesis about the presence of an indigenous germplasm preserved in this region from the LGM period.

Background. Dagestan boasts a long tradition of apricot cultivation that resulted in a unique gene pool of this fruit tree. However, the potential of local apricot cultivars for breeding still remains poorly investigated. This fact validates the need for further research into apricot genetic resources in Dagestan.Materials and methods. The local breeding material of apricot (23 forms and 5 cultivars) underwent genetic evaluation. For convenience, all accessions were divided into 4 groups according to the origin of cvs. ‘Krasnoshchekiy’, ‘Krymskiy Medunets’, ‘Shalakh’, and ‘Bukhara’. Their genetic diversity was analyzed using 11 SSR markers. Polymorphism of SSR markers varied 2 to 10 alleles per locus (on average, 5 alleles per locus). The effective number of alleles (Ne) and the Shannon Diversity Index (I) showed low values for the set of accessions, which is typical for seedlings with shared parental forms in their pedigrees. The differences in Ne and I values between the most contrasting groups were insignificant: Ne = 2.719 and I = 1.085 for the Shalakh group versus Ne = 2.014 and I = 0.782 for the Krasnoshchekiy group.Results. A comprehensive study of the apricot collection showed greater numbers of heterozygotes in hybrid seedlings than the expected values, attesting to large genetic distances between the pairs of parents selected for crosses. The highest heterozygosity was observed in the seedlings from the crosses ‘Krymskiy Medunets’ × ‘Krasnoshchekiy’, ‘Krasnoshchekiy’ × ‘Krymskiy Medunets’, and ‘Krymskiy Medunets’ × ‘Khonobakh’.Conclusion. Clustering the accessions with the principal coordinates analysis and Bayesian analysis on the basis of their genotyping data made it possible to identify general patterns in the distribution of cultivars and seedlings, namely the concentration of seedlings next to their maternal parents. Two genotypes attributed to cv. ‘Bukhara’ were found to have different genetic origin.

Developing late-leafing genotypes is crucial for mitigating the impact of late-spring frosts in walnut cultivation. Marker-assisted selection (MAS) offers a rapid screening approach for walnut populations in breeding programs, addressing the long breeding cycle. This study aimed to validate Turkish molecular markers associated with leafing date in the Iranian walnut populations and to implement MAS to identify late-leafing genotypes. Two polymorphic SSR primers, ‘JRHR209732’ and ‘CUJ-RBO12’, were validated using 14 early- and late-leafing cultivars/genotypes. MAS was then implemented for a population of 91 Iranian walnuts from a breeding program. The results indicated the effective differentiation of the Iranian population using the markers from Turkey, suggesting genetic similarity between the walnut populations of the two countries. Furthermore, alleles with band sizes of 277 and 115 were associated with late-leafing, while band sizes of 289 and 92 indicated early-leafing. Phenological data over three consecutive years, along with SSR analysis, confirmed the validation and implementation of MAS. The SSR analysis identified 14 alleles across all accessions, with an average of 7 alleles per locus. High leafing time variation was observed in the studied population, and cluster analysis identified four major clusters, revealing similarities and dissimilarities among the accessions. Finally, genotypes ‘Ch35T12’, ‘ChLa1’, ‘ChFr2’, ‘ChFr3’, ‘Ped35T1’, ‘Ped35T4’, ‘PedLa1’, ‘PedLa3’, ‘PedOp1’, and ‘ChPed2’ were identified as late-leafing genotypes based on screening with late-leaf alleles.

Walnut (Juglans regia L.) is a highly valuable, popular nut crop in many regions of the world. An effective management and utilization of plant genetic resources requires their comprehensive study. The current research was conducted to evaluate the genetic diversity and relationship of three Russian walnut collections, which are geographically located in Eastern Europe (Moscow, Crimea, and Kuban regions). Additionally, walnut varieties from USA, France, Moldova, and Ukraine were included in the plant materials under study. Totally, 141 walnut accessions were genotyped with 12 SSR markers. The number of alleles per locus varied from four (WGA72 and WGA4) to 21 (WGA276), with an average value of 10 alleles per locus. The level of polymorphism in the Russian subset of walnut genotypes was characterized as relatively high compared to the worldwide walnut germplasm. The analysis of genetic relationship within the experimental walnut accessions set involved using structure analysis, principal coordinate analysis (PCoA) and Fst - analysis. The structure analysis revealed seven main clusters of genotypes. Clustering generally correlated with the geographical origin of the walnut accessions. The NBG (Crimean) collection showed a relatively high level of influence from Moldovan and Ukrainian genetic backgrounds and also showed impacts from western European germplasms. Kuban local varieties and accessions were divided into two independent groups which are distanced from Kuban accessions that have Central Asian ancestral backgrounds. All sets of walnut accessions from the Kuban are distanced from the other studied groups of genotypes according to PCoA analysis. The data may reflect possible borders of contact between Asian and European walnut gene pools, along the line from Crimea to the north and between the basins of Dnieper and Don rivers. The results of this study can increase the effectiveness of management strategies, utilization of walnut genetic resources, and their combined applications in breeding.

Background. The development of genetic certificates and nomenclatural standards for newly released cultivars of Malus domestica Borkh. (apple tree) ensures an opportunity to preserve the original and authentic genetic and morphological information on domestic cultivars promising for the south of Russia. The purpose of this study was to develop genetic certificates and nomenclatural standards for 7 apple-tree cultivars developed at the North Caucasian Federal Scientific Center of Horticulture, Viticulture, Wine-making (NCFSCHVW), five of which were released jointly with the All-Russian Research Institute of Fruit Crop Breeding (VNIISPK).Materials and methods. The materials included apple-tree cultivars resistant or immune to scab (Venturia inaequalis (Cooke) G. Winter) from the NCFSCHVW collection stock. Conventional herbarization and DNA fingerprinting methods were used. For cultivar certification, an improved technique of DNA sampling and 12 microsatellite markers were applied.Results. Unique DNA profile certificates and nomenclatural standards were produced for 7 apple-tree cultivars: ‘Vasilisa’, ‘Karmen’, ‘Krasny Yantar’, ‘Soyuz’ and ‘Rassvet’ (with the Rvi6 gene) released jointly by the NCFSCHVW and VNIISPK, plus ‘Zolotoye Letneye’ and ‘Feya’ developed at the NCFSCHVW. The apple-tree herbarium specimens were placed for perpetual storage in the WIR Herbarium of the N.I. Vavilov All-Russian Institute of Plant Genetic Resources (VIR).Conclusion. The results obtained are promising for identification and authenticity verification of new domestic apple-tree cultivars during their reproduction and cultivation.

Recently, the task of updating the walnut assortment with new adaptive and high-quality varieties of domestic breeding has been solved, since foreign varieties cannot fully realize their biological potential in the conditions of the North Caucasus. In order to solve the issue of import substitution, it is necessary to create competitive, highly productive varieties with lateral fruiting, adaptive to unfavorable factors. At the same time, an extremely important characteristic of the variety is the quality of the fruit. The article presents the results of research on the search for promising forms of walnut. During the route trips, a preliminary assessment of the studied samples was carried out for the presence of lateral fruiting and fruit load, as a result of which 11 promising forms were identified for assessing the morphometric characteristics and quality of the fruits. All 11 selected forms of walnut are valuable for breeding and can serve as sources of economically useful traits (lateral fruiting, large fruit, high percentage of kernel yield, light, well-filled kernel, thin shell). Forms № 1, № 3, № 4, № 5, № 6, № 7, №. 8, № 10 can be considered the most promising in terms of the complex of phenotypic characteristics of fruits. These samples have an average (№ 1, № 5, № 7, № 8) and high (№ 3, № 4, № 6, № 11) percentage of kernel yield, good kernel extractability, kernel completion and can be used in breeding work, such as sources of economically valuable traits.

Methodological features of the main clonal micropropagation stages of plum PK SK 1 clonal rootstock (of NCFSCHVW selection) are described. The rootstock is characterized by a high adaptability to soil and climatic conditions of the region. In particular, it exhibits good winter hardiness, resistance to overwatered soils, tolerance to drought, and the capacity to grow on heavy soils. Plum seedlings on this rootstock develop a powerful root system. These advantages render the development and improvement of methods for clonal micropropagation of plum PK SK 1 clonal rootstock highly relevant. The research was carried out in 2019-2022. The period of active shoot growth, i.e., the first and second decade of may, was established to be the most optimal period for introduction of explants into in vitro culture. In this period, regeneration reaches 78.1–93.8 %. Eff ective shoot multiplication proceeds on MS medium with Fe-EDTA or MS medium with Fe-EDDHA and 6-BAP in the amount of 1 mg/L, with the highest number of shoots formed from one explant following the fourth passage (on average, 11.7 and 12.3 shoots per explant). A signifi cant eff ect of the 6-BAP concentration on the number of shoots formed was observed. The combined eff ect of the form of chelated iron and 6-BAP concentration on the number of shoots formed was established only after 3-5 passages on MS medium with Fe-EDDHA. The rooting stage of PK SK 1 rootstock can also be carried out on a hormone-free MS medium with Fe-EDDHA. The rooting effi ciency reaches 57.1–61.8 %. On average, 2.4 roots are formed per shoot with a length from 1.2 to 5.1 cm, with the root quality being high (not cartilaginous and not brittle). For the adaptation stage, rooted shoots with a height of at least 2 cm having two or more roots with a length of at least 2-3 cm are selected. A mixture of the Agrobalt plant nutrient soil, vermiculite, and perlite in a ratio of 3:1:1 can be used as a substrate. Following four weeks of adaptation, the number of adapted plants averaged 87.5 %.

Background. Cultivation of scab-resistant apple cultivars with better fruit storability increases the economic efficiency and environmental friendliness of horticulture. Hence, the development of such cultivars is an important task in modern apple-tree breeding. Materials and methods. A set of 646 hybrid plants obtained in six cross combinations (Renet Simirenko/Modi, Renet Simirenko/Smeralda, Renet Simirenko/Renoir, Renet Simirenko/Fujion, Renoir/Granny Smith, and Modi/Granny Smith) was studied. Their scab resistance was assessed under natural infection pressure for two years using a quantitative scale. The Rvi6 gene was identified using the PCR analysis with the primer pair VfC1+VfC. The Md-ACS1 gene alleles were detected with a known SCAR DNA marker. The chi-square test was applied for statistical confirmation of the data. Results. Based on the DNA marker analysis, 328 plants carrying the dominant allele of the Rvi6 gene were identified. The results of the phenotypic resistance assessment confirmed the correspondence of the resistant phenotype / dominant allele of the gene for most plants. Molecular genetics analysis of the Md-ACS1 gene disclosed its allelic combinations. A total of 190, 322, and 126 plants carrying allelic variants of Md-ACS1-2/2 , Md-ACS1-1/2 , and Md-ACS1-1/1 , respectively, were identified. Among the plants with the dominant allele of the scab resistance Rvi6 gene, 92 plant forms were identified with Md-ACS1 -2/2, and 143 heterozygous ones ( Md-ACS1-1/2 ), also valuable for breeders. Conclusion. A wide range of apple breeding forms carrying valuable alleles of the Rvi6 and Md-ACS1 genes were selected. Hybrid forms with target alleles of both genes responsible for important agronomic traits would contribute to the intensification of breeding efforts aimed at producing scab-resistant apple cultivars with increased fruit storability. They can also be used for breeding purposes as complex donors.

Micropropagation is a widely used method of plant propagation in the world, incl. rootstocks of fruit crops. Although methods are generally well developed, problems often arise in the process of work, which are mainly associated with the individual characteristics of the genotypes propagated in vitro. Therefore, for each variety and rootstock, an individual study of all stages of reproduction is necessary. In the course of this work, the influence of the chelated form of iron on the propagation rate and rhizogenesis of the rootstock for stone fruit crops PK SK 1 was assessed. At the stage of micropropagation, Fe-EDDHA (6 %, 100 mg/l) and 6-BAP (0,5 mg/l; 0,75 mg/l; 1,0 mg/l). Fe-EDTA (0,5 mg/l; 0,75 mg/l; 1,0 mg/l) was used as a control. On the medium with the addition of Fe-EDDHA and 6-BAP in the amount of 0,75 and 1,0 mg/l, 9-10 new shoots are formed from one explant, which is 11-28,6 % higher than on the medium with Fe-EDTA. Also, on the medium with Fe-EDDHA, 13–26 % less vitrified shoots are formed. At the rooting stage, the usage of Fe-EDDHA (100 mg/l) with IBA 1,0 mg/l and 2,0 mg/l in the medium makes it possible to increase the rooting of plants by 12,1 and 26,9 %, respectively. On a hormone-free medium (without IBA) containing Fe-EDDHA 100 mg/l and 200 mg/l, 43,8 and 48,5 % more plants rooted than on a hormone-free medium with Fe-EDTA.

The article presents the results of a morphometric evaluation of nuts of 10 hybrid walnut forms according on 13 characteristics (weight of the unshelled nuts and kernel, nuts size, kernel yield, kernel color, kernel completion, extractability, shell structure, shell thickness, septa thickness, shape). Set of samples with a complex of breeding valuable traits, was selected according to obtained results.

Walnut is an important horticultural crop, the production of which ranks second among all nut crops. Despite the significant demand in the domestic market in Russia, the industrial production of walnut fruits in Russia is currently underdeveloped. At the same time, there is a need to update the assortment with new highly productive varieties adapted to local agro-climatic conditions and having high quality nuts that are competitive at the world level. An important issue for the successful implementation of breeding programs is a comprehensive study of the gene pool. In this regard, within the framework of the study, the task was to evaluate promising varieties from the collection of the walnut gene pool of the Nikitsky Botanical Gardens and analyze genetic relationships based on microsatellite genotyping. On the basis of the performed phenotypic assessment, the study sample, which included 31 varieties, was divided into several groups according to the main phenotypic traits, such as frost and drought resistance, the start of the growing season, the ripening period, the weight and type of flowering, the weight of the fruit, and the thickness of the endocarp. Varieties with economically valuable traits that can be recommended as promising as initial parental forms in breeding work for resistance to abiotic stress factors have been identified, as well as varieties with increased productivity and large fruit sizes. Based on the analysis of eight SSR markers (WGA001, WGA376, WGA069, WGA276, WGA009, WGA202, WGA089 and WGA054), an analysis of the level of genetic diversity was performed and genetic relationships were established in the studied sample of varieties. Six (for WGA089) to eleven (for WGA276) alleles per locus have been identified. A total of 70 alleles were identified for the eight DNA markers used, with an average value of 8.75. Analysis of SSR genotyping data using Bayesian analysis established the presence of two main groups of genotypes. Taking into account the fact that all the studied varieties are selections from local seed populations in different regions of the Crimean Peninsula, the revealed level of polymorphism may indirectly reflect the level of genetic diversity of the local walnut populations. Furthermore, the presence of two genetically distant groups indicates the presence of two independently formed pools of the autochthonous gene pool of the species Juglans regia L. on the Crimean Peninsula.

promising genotypes in the areas where this species grows. The identification of the valuable breeding forms of English walnut among local seed populations facilitates the solution of breeding problems and replenishes the collections of genetic resources with valuable specimens. In this work, we aim to assess the prospects of using new forms to solve breeding problems by means of phenotypic evaluation and molecular genetic analysis. The search for promising forms was carried out in 2022–2023 on the territory of settlements in the different districts of Krasnodar Krai. Economically valuable traits were recorded according to the “Program and Procedure for the Studying the Varieties of Fruit, Berry, and Nut Crops.” In order to assess the level of genetic diversity in the sample of new, promising forms of English walnut, SSR genotyping was carried out using seven microsatellite DNA markers: WGA001, WGA376, WGA069, WGA276, WGA009, WGA202, WGA089. The heterogeneous group of varieties and elite breeding forms of the North Caucasus Federal Scientific Center of Horticulture, Viticulture, and Winemaking, representing the overall diversity of the collection, was also included in the studied sample. The comparison of the polymorphism level in the studied specimens for both individual markers and the entire sample of markers suggests a relatively high heterogeneity of the new, promising forms included in the study. The use of UPGMA, PCoA, and analysis in STRUCTURE software allowed genetic relationships to be established between the new, promising forms and specimens from the genetic collection of the North Caucasus Federal Scientific Center of Horticulture, Viticulture, and Winemaking. The new forms were found not to form a separate cluster and to generally have an intermediate position between the three genotype groups in the gene pool collection. For the new forms, the effect of the Central Asian geneplasm was established, which determines the presence of several valuable breeding traits. Given the data on the genetic diversity of new, promising forms of English walnut relative to the genetically contrasting sample of breeding forms from the collection of the North Caucasus Federal Scientific Center of Horticulture, Viticulture, and Winemaking, it is reasonable to involve new forms in breeding in order to enrich the local English walnut gene pool.

РАЗРАБОТКА МЕТОДА МУЛЬТИПЛЕКСНОЙ ИДЕНТИФИКАЦИИ ВИРУСА ШАРКИ СЛИВЫ И

Citrus is one of the most widely grown fruits worldwide, cultivated in over 130 countries, primarily in tropical and subtropical climates. Implementing successful and dependable breeding programs is crucial for addressing rising demands for adequate fruit performance and productivity. Our understanding of plant reproductive biology has advanced significantly in recent years, attributable to research on model plants. However, knowledge gained from these species cannot always be applied to citrus, owing to the fact that citrus is a perennial tree crop with distinctive reproductive biology. The growth and development of citrus fruits is a complex process impacted by a range of internal and external stimuli that could operate sequentially or concurrently. In the field of citriculture, plant growth regulators have become a crucial facet in increasing productivity by improving fruit sets and flowering. Plant growth-regulatory compounds actively regulate growth and development by controlling endogenous processes and altering the growth response exogenously. Different PGRs are also employed to expedite maturity, delay harvest, and retain fruit quality after harvest. The current review compiled comprehensive, up-to-date information on the role of plant growth regulators in flowering and fruit set during various stages of growth and development, as well as the ripening process in citrus, by bringing together the scientific and technical literature published on the PGRs subject with a focus on physiology and advancement in molecular biology from the beginning to till date. It will ultimately provide valuable information to researchers, particularly those involved in horticulture research, particularly fruit tree genetics and breeding.

Введение.Грецкий орех (Juglans regia L.) является одним из самых потребляемых орехов в мире благодаря

Apple (Malus x domestica Borkh.) belongs to the family Rosaceae, extensively cultivated, consumed, and cherished fruit in the world due to its various nutritional values and extensive health advantages. However, due to crop's perennial nature, extended juvenile period, heterozygosity, and sexual incompatibilities, conventional apple breeding or genetic improvement is a very difficult and time-consuming procedure. So, identifying spontaneous mutants/bud sports and multiplying them asexually may be used as a prompt and efficient approach for developing new apple cultivars. To date, substantial number of apple mutant cultivars are being grown across the world, and a significant number of new variants may evolve each year that are either disregarded or unnoticed by individuals. For the first time, we have summarized the phenotypes and regulation mechanism of bud sports in apple including fruit peel color development, flowering time and fruit maturation time etc., and also summarized the molecular identification method of bud sports along with epigenetic regulation that eventually led to the enormous gene pool diversity based on variations in phenological, biochemical, and organoleptic characteristics over their parents. This paper provides useful and contemporary information in one place for the researchers those working in the area of horticulture research particularly apple genetics and breeding.

ОПТИМИЗАЦИЯ МЕТОДА ПЦР-ДИАГНОСТИКИ ВИРУСА ШАРКИ СЛИВЫ Федорович Святослав Валерьевич младший научный сотрудник лаборатории вирусологии Супрун Иван Иванович канд