Relevance. The presented studies are aimed at obtaining new forms of tomato with a complex of genes for resistance to fungal diseases in combination with a standard type of bush and dark coloring of fruits based on marker-mediated selection.Methodology. The biological objects of the study are varieties and hybrid forms of tomato from the collection of the Michurinsky SAU. Molecular genetic analysis was performed using the following methods. DNA extraction was carried out from young leaves using a kit for isolation of NC Sample NC manufactured by Agrodiagnostika LLC according to the manufacturer's protocol. Fermentas production kits were used for PCR. Identification of the cladosporosis resistance gene was Cf-19 performed using the DNA marker R7. The presence of a fusarious wilting resistance gene was determined by a I-2/5 marker. The amplification results were visualized by agarose gel electrophoresis.Results. During the research, a collection of varieties and hybrid forms of tomato of the Michurinsky GAU was analyzed in order to identify genes for resistance to cladosporiosis Cf-19 and fusarium wilt I-2. A total of 52 genotypes were analyzed. It was found that most samples (41 samples) are characterized by a heterozygous state of the Cf-19 gene. All indeterminant and semi-determinant forms had both alleles. Of the 23 determinant forms presented in the collection, 10 had only one allele corresponding to recessive homozygote. Among all analyzed tomato genotypes, no dominant homozygous forms were noted. The study of the collection revealed several alleles of the I-2 gene. In total, four fragments corresponding to various alleles were amplified. A total of 50 resistant genotypes have been identified in the collection. Two alleys of the I-2 gene (633/693 bp) were identified in 42 tomato samples. Four varieties are homozygous in one allele (633 bp), which determines resistance. Three varieties have a second resistance allele (566 bp). One genotype has only an allele defining susceptibility (693 bp). On the basis of molecular analysis, as well as an assessment of the type of bush and fetal color, initial forms were selected with subsequent hybridization. 67 hybrid tomato plants were obtained. Evaluation of the presence of resistance genes showed that most of the resulting hybrids are resistant to cladosporiosis and fuzariosis. This is due to the presence of dominant alleles of Cf-19 and I-2 genes in a heterozygous state. Among the resulting hybrids, plants with a bark type of bush were identified. A total of 13 such plants were obtained.Conclusion. Thus, the work carried out allowed to obtain hybrid forms of tomato combine the signs of resistance to two pathogens of fungal diseases and the stem type of the bush. These forms are planned to be used in further selection work.

Molecular genetic analysis revealed a polymorphism for the Md Exp7 gene that controls the bio synthesis of expansin in wild species of the genus Malus. Eight allelic forms of the gene were identified, four of which were unique. The regularities in the allele distribution in 37 genotypes were found to be in accor dance with their systematic positions. The trait was found to be broadly diverse both among the sections of the genus and within a particular section. Variants of the gene were identified in representatives of one species.

At Pushkin and Pavlovsk Laboratories of the N.I. Vavilov All-Russian Institute of Plant Genetic Resources (VIR) a diverse collec tion of local apple cultivars is maintained. Some of the cultivars are widely used in breeding programs for their ecological plasticity, increased adaptation to abiotic stress and disease resistance, still there have been no large-scale studies of these local cultivars for fruit storage ability. Fruit softening during storage is an important problem for apple production. Retention of desirable firmness after prolonged storage is one of the key requirements for new apple cultivars. Expansin and ethy lene biosynthesis related genes are known to be involved in control of fruit softening in apple, and gene specific molecular markers have been reported. In this study the polymorphism and allelic configuration of ethylene and expansin biosynthesis related genes Md-ACS1, Md-ACO1 and Md-Exp7 involved in control of fruit softening in 87 local apple cultivars from VIR Collection of Plant Genetic Resources were analyzed. PCR markers Md-ACS1, Md-ACO1 and SSR-marker Md-Exp7 were used in the study. The allele frequencies in the collection generally coincided with the data from previous studies. Md-ACS1 allele 2 associated with reduced ethylene production was found only in three local cultivars, while all the studied local cultivars were heterozygous for the Md-ACO1 locus, as well as most modern Russian apple cultivars. Half of the studied local cultivars were heterozygous for Md-Exp7 (198 : 202). Thirteen local cultivars with rare Md-Exp7 alleles (206, 210 and 212) were detected. No association was found between the Md-Exp7 genotype and the cultivars’ maturation time. The obtained results can be used for additional evaluation of the cultivars’ potential for breeding.

Breeding work in the Michurinsk State Agrarian University (MSAU) is based on one of the eff ective strategies for producing high-quality planting material for establishment of intensive perennial fruit plantations – the use of apple varieties and clone stocks that are highly resistant to extreme factors and immune to diseases. As a result of many years of breeding work, the MSAU is the originator of 24 forms of clonal stocks (out of 46 forms allowed for cultivation in the Russian Federation) and the patent holder of 8 stocks. In 2018, 4 apple clonal rootstocks (70-20-20, 70-20-21, 71-7-22, 75- 1-62) were included in the State Register of Breeding Achievements admitted to cultivation on the territory of the Russian Federation. The main requirements for apple stocks for intensive orchards are high resistance to major environmental factors; suitability for intensive types of orchards; increased resistance to pathogens; good ability to vegetative propagation; lack of root shoots in the orchard; increase of productivity, early fruited varieties, quality of fruits. The advantages of planting material of apple trees on weak clonal rootstocks of the MSAU breeding are established: high compatibility of rootstocks with the best zoned and promising apple varieties; high frost resistance and winter hardiness of the root system, withstanding up to -16 °С – there are no foreign analogues on this basis; high resistance of stocks to the bacterial burn (unlike most foreign stocks); accelerated entry into fruiting, the onset of the period of commodity bearing fruit in the orchard on the 3rd ... 5th year; high productivity of commercial apple plantings in the conditions of Central Russia – an average of 25 to 40-50 tons / ha. For widespread introduction into production, the most studied clonal stocks of the MSAU breeding are recommended in Russia and in many countries of the world: the Paradizka Budagovsky (dwarf), 62-396 (half-dwarf), 54-118 (medium-sized). To increase the productivity and the resistance of plants and the eff ectiveness of Russian horticulture as a whole, it is necessary to create mother nurseries of apple rootstocks, free from harmful viral infections (repositories).

Background. Leaf mold, a disease caused by the fungus Cladosporium fulvum Cooke in tomato, is one of the reasons for a significant decrease in the fruit yield. The most reliable and environmentally friendly way to protect tomato from diseases is the development of resistant cultivars and hybrids. The study of genetic aspects of disease resistance in plants is the basis of successful breeding work. Markerassisted selection of the source forms of tomato is a relatively new approach in breeding, based on direct selection of plants for genes that determine the economically important traits. It allows for the time-saving analysis of breeding material. Materials and methods. The present work offers the results of screening more than 30 accessions from the genetic collection of tomato cultivars and hybrids of the Michurinsk State Agrarian University using the P7 molecular marker. Results and discussion. Polymorphism of the Cf-19 gene of resistance to leaf mold was evaluated, and clear reproducible results were obtained. To test the marker, seven hybrid forms of greenhouse tomato were used. The reliable identification of the Cf-19 gene by using the P7 marker was confirmed through artificial infection with C. fulvum. Six out of seven hybrids demonstrated a high level of resistance to the pathogen, which is confirmed by the originators' data. A strong lesion was noted on the leaves of only one hybrid. The molecular genetic analysis has shown that among all control samples, only this genotype was a recessive homozygote. Besides, according to the originator, this genotype is not resistant to leaf mold. The performed test proves the high efficiency of the P7 marker. By using it, 35 genotypes were analyzed. The data obtained during the work show that the majority of the studied samples turned out to be heterozygous. At the same time, homozygous forms were also noted. For instance, the 'Golden Rain' tomato cultivar has only one 250 bp fragment, which corresponds to a recessive homozygote. Four genotypes were found to contain 300 bp fragments, which correspond to dominant homozygotes. The molecular genetic analysis revealed a number of genotypes that can be used as sources of resistance to leaf mold.