This overview substantiates the possibility and expediency of blackberry breeding in Central Russia, where it is in demand, but not widespread in horticulture. Significant achievements of world breeding, which gave modern cultivars a large set of economically important qualities and growing interest in it all over the world, including Russian gardeners, make it relevant to work with blackberries as an object of selection, and as a promising garden plant. However, insufficient frost and winter hardiness of the bulk of the cultivars of this culture cause certain difficulties when growing it in the areas with cold winters to which the Central zone of Russia belongs. The expansion of the market of berry products also imposes increasingly high requirements on the complex of economic indicators of new cultivars, primarily the quality of blackberry fruit. In this regard, improving the existing range of varieties of the culture, increasing its adaptive properties and commodity qualities of berries are urgent tasks for breeders when creating new cultivars. The relevance of blackberry breeding is also dictated by the fact that in Russia its domestic range of varieties is represented by only one modern cultivar obtained in the southern region and adapted, first of all, to it. For the Central zone of the country, the cultivars of this plant have not been developed (except for the limited experiments of I.V. Michurin conducted almost 100 years ago). Therefore, the breeding of adapted cultivars of the culture in the climatic conditions of this region may be promising. It is also possible to grow here (with shelter for the winter) the cultivars already created abroad that can give with the right agricultural technology a good industrial harvest, which is confirmed by the practice of amateur and farm gardening, as well as scientific research. The purpose of this work is to designate the leading directions of blackberry breeding, the most important in the conditions of Central Russia and to show prospects of the development of new cultivars of this valuable culture in the specified climatic zone. The analysis of world trends and experience in the blackberry breeding and variety study, as well as the results of our own research of the culture conducted in the Orel region, allow us to consider it promising and relevant to work on improving the range of varieties of this plant in Central Russia. All priority areas of blackberry breeding, indicated in foreign and domestic breeding programs (winter hardiness, high quality of fresh and processed fruit, the correct shape of berries, their large size, the necessary values of biochemical composition, high productivity of plants, thornless shoots and high resistance to diseases and pests), are relevant for this region of our country, while high winter hardiness is currently the most important of them.

The features of pollen grains sculpture of 8 cultivars Rubus fruticosus L. have been studied in details via the scanning electron microscope method. The pollen material picked up in the Central region of Russia and the Republic of Adygeya has been used in the research. The comparative data of morphometric factors are presented, the polymorphism of pollen grains-size and surface is determined. The complex sculptural types are formed by the different combination of 2 or 3 simple sculptural types. The complex structural type of exine is characteristic of the studied cultivars Rubus fruticosus. The average size of pollen grains polar axis is within 32.43-37.46 µm; the equatorial diameter is within 16.91-18.88 µm. The ratio of polar and equatorial axis (Р/Е) marks the degree of the pollen grains elongation (roundness). The research showed that the cultivation region gives a certain influence on the change of the pollen average dimensions, but it does not influence P/E ratio. The pollen grains form is oblong-ellipsoid. In the polar outline the grains are round. The pollen grains of the presented blackberry cultivars are 3-or 4-colporate, the apertures are long. The sculpture of the pollen grain exine is complex, it belongs to the two component sculptural type-rugulose, the picture has the species features. The morphometric and sculptural identical characteristics are separated: the form (the pollen grains elongation degree), the dimensions (the ratio of the polar axis to the equatorial axis (P/E), the number of apertures and the surface picture (microstructure).

The taste characteristics of berries of 26 cultivars, elite and selected forms of blackberries grown in Central Russia are presented: dry matter, monosaccharides, sucrose acid the total amount of sugars. The sugar-acid index has been calculated. The best genotypes have been identified according to the content of dry matter and sugars - Brzezina and Agawam cultivars, elite seedlings LN-4, LN-13, LN-14 and selected seedlings LN-5, LN-7, LN-8, according to the content of organic (titrated) acids and sugar-acid index - Brzezina, Black Satin, Loch Tau, seedlings of Black Satin, Cheyenne, Loch Ness - LN-6, LN-10, EV LN-13 and control cultivar Agawam. A high traits’ conjugation was established: the sugar-acid index and the content of monosaccharides, the total amount of sugars, soluble solids, as well as a high inverse dependency between the content of organic acids and the sugar-acid index. Low unreliable correlation coefficients (r = - 0.28 … + 0.13) were obtained, indicating the absence of links between the fruit weight and the content of biochemical components responsible for the taste characteristics of genotypes, which is a positive fact when creating new cultivars with high taste and a significant weight of fruits, indicating their independent inheritance.

The article deals with the main morphological groups of blackberries — erect, trailing and intermediates — semi-erect and semi-trailing. The nature of shoots’ growth and the way of natural vegetative reproduction were used as the basic criteria for this grouping, which together reflect the polymorphism of the plant being one of the adaptability indicators to different growth conditions. The expediency of such division for grouping of the existing blackberry cultivars’ diversity with complex genetic origin was substantiated. As an additional criterion of this grouping, the shoots growth dynamics of morphological groups’ typical representatives has been studied, which shows their differences during vegetation and in transition to period of plants’ rest. In the phase of growth completion, the differences between group representatives were particularly clear: erect are characterized by early completion of growth processes, trailing do not finish them until the end of the growing season, semi-trailing/semi-erect complete growth in the term in between the first two groups. There is a difference in winter resistance of old erect cultivars and more modern members of this group of blackberries with different genetic origin; the latter’s significant advantages are noted due to their thornlessness and lack of abundant growth. The role of plants’ habitus of the main morphological groups’ representatives for their cultivation in the conditions of the middle zone of Russia and, first of all, for overwintering cultivars; the value of both erect primocane-fruit cultivars and trailing - less winter-resistant, but the most convenient for winter shelter by habitus.

Background. Blackberry is becoming increasingly popular in Russia for its rapid early-fruiting, high self-fertility and late flowering, contributing to longer consumption of fresh berries, a source of antioxidant compounds. There is a need to study the biochemical composition of blackberries.Materials and methods. Fruits of 25 blackberry cultivars and hybrid seedlings from the Institute of Fruit Crop Breeding (VNIISPK) were analyzed for the contents of catechins, leucoanthocyanins, anthocyanins, and total phenolic compounds using the photometric method, and the content of ascorbic acid using the titrimetric method. Statistical data processing was carried out using the methods of variation and correlation analyses.Results. Bioactive compounds (BAC) accumulating in blackberry fruits were studied: ascorbic acid, catechins, leukoanthocyanins, anthocyanins, and total phenolics, with medium and significant variability of the studied indicators (V > 10%). Among the genotypes, 73% accumulated more than 20.0 mg/100 g of ascorbic acid in fruits. All genotypes were identified as sources of anthocyanins. About 50% of the accessions accumulated catechins in fruits above the average level. Leucoanthocyanins were stored in blackberry fruits in slightly larger amounts than catechins. In 10 accessions the level of phenolics was higher than 1000.0 mg/100 g.Conclusion. Genotypes with high BAC content were identified. Correlation coefficients were obtained: they indicate the presence of an medium degree of rectilinear relationship between the content of ascorbic acid and anthocyanin compounds, ascorbic acid and total phenolics. Cvs. ‘Black Satin’, ‘Cacanska Bestrna’, ‘Chester’, ‘Natchez’ and ‘Triple Crown’, plus hybrid seedlings LN-14, LN-1 and LN-7, were identified according to a set of indicators (ascorbic acid and phenolics) and recommended for breeding to improve the quality of blackberry fruits.