This review presents an analysis of the literature, which indicates the popularity of breeding methods in the fight against oomycete and fungal diseases of tomato: late blight (pathogen − Phytophthora infestans (Mont.) de Bary), fusarium wilt (pathogen − Fusarium oxysporum f. sp. lycopersici (Sacc.) Snyder and Hansen), early blight or alternariosis (pathogens − representatives of the genus Alternaria), cladosporiosis (pathogen−Cladosporium fulvum Cook.). Theoretical and practical achievements, the latest developments in genetics, molecular biology, plant physiology, microbiology are considered. Special attention is paid to modern information about the diversity of tomato pathogens, their morphological, genetic, physiological features, including racial composition; the presence of pathogen resistance genes in the gene pool of the culture under study, their mapping and the possibility of introduction into the genome from other sources; about the developed markers of target genes and loci of quantitative traits; the degree of associations between a molecular marker and a target gene; about the features of inheritance of the studied trait, as well as the possibility of pyramiding R-genes and QTL in one genotype. To accelerate and improve the efficiency of tomato breeding for resistance to pathogens, these issues are of great importance. Their study will strengthen the integration of modern biotechnology with the traditional breeding process, which is carried out by classical methods.

Relevance. The studies are aimed at assessing the intravarietal allelic diversity of genes for resistance to fusariosis and cladosporiosis of tomato cultivars bred at the Michurinsky State Agrarian University using molecular markers.Methods. The biological objects of the study are tomato varieties bred at the Michurinsky State Agrarian University. A total of 10 varieties were analyzed. The assessment of intravarietal polymorphism was determined on a sample of 10 plants of each variety. DNA extraction was performed using a Quick-DNA Plant/Seed Miniprep Kit (Zymo Research, USA) for DNA extraction according to the manufacturer's protocol. The P7 DNA marker was used to identify the cladosporosis resistance gene Cf-19. The presence of the fusarium wilt resistance gene I-2 was determined using the marker I-2/5. Amplification results were visualized by electrophoresis in 2% agarose gel.Results. 10 plants of 10 varieties of Michurinsky GAU selection tomato were analyzed using molecular markers of genes for resistance to cladosporiosis and fusariosis. An assessment of intravarietal polymorphism was carried out. In most of the varieties studied, the genes analyzed are identified in a heterozygous state. Three varieties (Vivat, Carotinka, Krasavets) containing only alleles of susceptibility to the causative agent of the disease in the genotype I-2 identified by the gene. Individual samples were homozygous for the fusariosis resistance allele. Analysis of the gene for Cf-19 resistance to cladosporiosis showed that most of the varieties studied are heterozygous forms. In some varieties, all ten plants were heterozygous. These include Krasavets, Vivat, Orlik, Bui Tour. The remaining samples had different allelic compositions. The pathogen resistance allele has been identified in plants of the Nepryadva and Chernysh varieties. The dominant allele in the homozygous state was detected in the Japanese variety. At the same time, all the analyzed plants of this variety were monotonous.Conclusion. It has been established, but a significant part of the varieties of tomato selection of Michurinsky GAU is polymorphic in the genes for resistance to cladosporiosis and fusariosis. In this case, a significant part of the varieties can be used in selection during preliminary molecular analysis. According to the gene for resistance to fusariosis, the following varieties are identified sources of the resistance allele: Sokol, Nepryadva, Yaponchik, Orlik, Zolotnichok, Chernysh. In them, the gene is I-2 represented in a heterozygous state. Intraortic polymorphism was also noted for the Cf-19 gene. Most samples have two alleles. The exception is the Japanese variety, which is the dominant homozygote for this gene.

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.