The leaf rust (Puccinia recondita f. sp. tritici Rob. Ex Desm.) is one of the most common and harmful wheat diseases. The disease leads to significant losses of grain yield (Novohatka, 1979). The level of wheat yields loss to 30% during the epiphytotic rust according to the Food and Agriculture Organization of the United Nations (FAO) (El-Khoury, 2009). The population of the pathogen Puccinia recondita differs from the high adaptive ability. High variability virulence of the fungus leads to the accumulation of pathogens that capable of the genes of wheat resistance (Palamarchuk et al., 2019).

The most justified, economically sound, and environmentally safe method of fighting to disease is to creating resistance varieties. The effectiveness of breeding to rust resistance can be improved by using different Lr – genes (Zheplinska et al., 2019).

More than 90 resistance genes to the rust-leaf pathogen are identified and characterized by chromosomal localization and efficiency at the wheat genome and its relatives (Kovalyshyna and Dmytrenko, 2017), which information is collected annually and is published in the Catalogue of gene symbols for wheat (McIntosh et al., 2003a; McIntosh et al., 2007b; McIntosh et al., 2008c; McIntosh et al., 2009d; McIntosh et al., 2010e; McIntosh et al., 2011f; McIntosh et al., 2012g; McIntosh et al., 2014h; McIntosh et al., 2016i; McIntosh et al., 2017j; McIntosh et al., 2018k; McIntosh et al., 2019l). Most genes of resistance to rust causative agents identified in cultivars of wheat descend from their wild relatives. Thus, according to the information provided in the catalogs of genetic symbols, about half of the known resistance genes to leaf rust are allogenic, introgressive into Triticum aestivum species from different types of wheat, aegilops, wheat grass, and others (Leonova et al., 2013). The almost all effective rust resistance genes at the territory of Ukraine, except Lr10 and Lr23, are allogenic, transferred to Triticum aestivum from other species: Aegilops speltoides – Lr28, Lr35, Lr36, Lr47, Lr51, Lr66; Aegilops tauschii – Lr1, Lr21, Lr22a, Lr32, Lr39, Lr42; Triticum timopheevii – Lr18, Lr50; Thinopyrum elongatum – Lr19, Lr29, Lr24; Secale cereale – Lr25, Lr26, Lr45; Aegilops umbellulata – Lr19, Lr76; Triticum spelta – Lr44, Lr65, Lr71; Triticum dicoccoides – Lr53, Lr64; Aegilops triuncialis – Lr58, LrTr; Triticum timopheevii spp. viticulosum – LrTt1; Aegilops ventricosa – Lr37; Aegilops kotschyi – Lr54; Elymus trachycaulis – Lr55; Aegilops sharonensis – Lr56; Aegilops geniculate – Lr57; Aegilops peregrine – Lr59; Triticum turgidum – Lr61; Aegilops neglecta – Lr62; Triticum monococcum – Lr63. Therefore, in breeding must be taken into account the fact that in the wheat genome the effective Lr-genes are introduced not in its "pure" form, but closely linked with other genes that are undesirable to use in breeding (Dinh et al., 2020; Lodgering et al., 1970).

It is a rather difficult task creating such varieties, and over time, they lose their resistance by the emergence of new races, pathogenic strains, and climatic changes. Trends in climate warming affect on the deterioration of the phytosanitary condition of crops (Mushtruk et al., 2020).

The assessment varieties (Table 1) of winter wheat were created at the V. M. Remeslo Myronivka Institute of Wheat for resistance to leaf rust made in conditions of the artificial infectious background of the wheat pathogen. Experiments were in the field conditions at a field infectious nursery of the Plant Protection Department of the V. M. Remeslo Myronivka Institute of Wheat. The climate is temperate continental. The average annual air temperature is 7.6 °C. The sum of effective temperatures above 5 °C is 3000 °C. The duration of the frost-free period becomes an average of 165 days. The average annual amount of decline is 310 – 570 mm.

A suspension of a mixture of spores isolated from the local leaf rust population was used for inoculation. Wheat varieties were inoculated a mixture of spores with talc in the ratio of 1:100 by a technique of (Geshele 1971) in a tubing phase – beginning form ears in condition artificial infectious nursery. The spore load was 0.015 kg of urediniospores per one m² of sowing. The assessment of resistance was conducted dynamically every 10 days (Tkachyk, 2014). The variety Myronivska 10 was used as a susceptible standard. The accounts defeat by the causative agent were evaluated on the scale according to (Trybel et al. 2010) and (Bober et al. 2020). A DNA was isolated from weight 25 – 40 mg of the plant material, obtained by grinding of 5 grains in ceramic mortars to a homogeneous powder and the further selection and weighing (Babaiants, 2011). DNA isolation was conducted using sets of Diatom^TM DNA Prep100 (NEOGENE, Ukraine) according to a standard procedure with certain modifications (Trybel et al., 2010).

The caSNP12 marker was used in investigations of genetic material for identification allelic status of the resistance gene to wheat leaf rust Lr34, (Radchenko and Odintsova, 2008). PCR was performed on the amplifier GeneAmp® PCR System 2720 (Thermo Fisher Scientific, Massachusetts, USA) using sets GenPak^® PCR Core according to the manufacturer's method. The primer sequences are as follows: for caSNP12F – 5’-TCCCCAGTTTAACCATCCTG-3’; for caSNP12R – 5’-CATTCAGTCACCTCGCAGC-3’ (NEOGENE, Ukraine).

The conditions of the PCR were in line with the requirement recommended by the developer. As a result of PCR with a mixture of primers flanking the caSNP12 marker (Strahov, 1951). The stable allelic state of the markers (- Lr34 +) answered amplicons with a length of 234 p. n., the sensitivity was the absence of amplicons (Vyerchenko et al., 2019).

Fragments received from PCR were separated in 1.8% agarose gel. Ethyl bromide was used as an intercalating agent for DNA monitoring in an ultraviolet. The system VISION Gel (Scie-plas, Great Britain) was used for gel documentation. The length of the clearest and reproducible bands was determined using DNA marker O’Gene Ruler 50 bp Plus DNA Ladder (Fermentas, Lithuania).

The genes of high efficiency against the pathogen are Lr9, Lr19, Lr37, Lr42+Lr24, Lr43 (Lr21+Lr39) +Lr24, Lr9+L26, Lr10+Lr24 discovered by investigation the population of leaf rust on varieties of carriers of effective resistance genes (Leary et al., 2018; Ramanathan et al., 2018). The resistance of the varieties protected by the Lr24 genome is lost. We observed a slight defeat by the pathogen of the carriers of the Lr19 gene, indicating that the population has virulent clones against it. The pustules of leaf rust were marked also on varieties protected by the genome Lr9 in some years. The genes Lr37, Lr42 + Lr24 and Lr43 (Lr21 + Lr39) + Lr24 have high efficiency in recent years. The Lr13, Lr34, Lr37 genes provide the longterm protection of wheat against rust in combination with other genes (Dorofee, 1972; Bharti et al., 2016). The varieties with these genes remain resistant for 20 – 30 years in different countries of the world (Leppik, 1970).

10 highly resistant endemic species of wheat and its relatives with the highest immunity to rust, in particular: Triticum monococcum, T. timopheevii, T. militinae, T. Zhykovski, T. fungicidum, Haynatriticum, Aegilops umbellulata are distinguished (Varella et al., 2017; Jafary, Szabo and Niks, 2006).

In the works (Casey et al., 2016; Marryat, 1907; Davoyan et al., 2012) found forms immune to rust, powdery mildew, and soot among Triticum dicoccum.

The principles of researching gene pool of wheat resistance against leaf rust, based on (Flor, 1971) theory of "gene-for-gene", developed (Berlyand-Kozhevnikov et al., 1985).

In Ukraine, wheat breeding for rust resistance is conducted for more than 40 years. Scientific researches on the study of genetic signs of resistance to the causative agent of leaf rust actively unfolded in the late 70's – the early 80's of the twentieth century (Morgounov et al., 2011). The greatest successes have been achieved at the V. M. Remeslo Myronivka Institute of Wheat of the National Academy of Agricultural Sciences of Ukraine, the Plant Breeding and Genetics Institute – National Center of Seed and Cultivar Investigation of the National Academy of Agricultural Sciences of Ukraine, the Institute of Plant Protection of National Academy of Agrarian Sciences of Ukraine and the Рlant Production Institute nd. a. V. Ya. Yuryev of National Academy of Agrarian Sciences of Ukraine (Khaneghah et al., 2018; Kirilenko, 2014).

We conducted researches on the detection of the resistance gene to leaf rust in winter wheat varieties of Myronivka's breeding. The 1BL/1RS wheat-rye translocation, which carries the resistance gene to leaf rust Lr26, as well as resistance genes to stem rust Sr31, powdery mildew Pm8, yellow rust Yr9 were found in the following varieties: Myronivska 61, Myronivska 27, Myrleben, Myronivska 28, Myronivska 30, Myronivska 31, Myronivska 33, Myrych, Myronivska 65, Myronivska 66, Kryzhynka, Myronivska 67, Vesta, Snizhana, Pereiaslavka, Demetra, Favorytka, Pyvna, Kalynova, Kolos Myronivschyny, Monotyp, Ekonomka, Myronivska storichna, Lehenda Myronivska according to the results of investigations by (Kovalyshyna et al. 2020), (Lisova 2012) and (You-Xiong et al. 2009). The Lr26 gene does not provide high resistance of varieties to leaf rust causative agent, since this gene has lost its effectiveness against the population of the disease as the data in Table 1 show.

The availability of wheat-rye translocation 1AL/1RS in the genotype of winter wheat provides resistance to fungal diseases, because it carries a complex of resistance genes – to leaf rust Lr24, stem rust Sr1RS, powdery mildew Pm17. This translocation was detected in varieties: Kolumbiia, Smuhlianka, Vesnianka, Zolotokolosa, Yasnohirka, Slavna, Yavoryna (Vlasenko, Koliuchyi and Chebakov, 2005; Landjeva et al., 2006). The Lr24 gene provides moderate resistance to leaf rust, varieties have damage of 2.8 – 17.2%.

The varieties Vesta, Snizhana, Demetra are protected by the Lr26 and Lr34 genes, and the Zolotokolosa – by the Lr24 and Lr34. The combination of these resistance genes inhibits the development of leaf rust on winter wheat varieties, damage of the leaf surface is within 10 – 17.5%

The Myrliena variety contains the gene Lr23, and the Myronivska storichna – Lr3, Lr23, Lr10, and Lr26 are ascertaining according to the analysis of the genealogy of varieties. The Lr3, Lr24 genes, protects the Ekonomka variety.

The gene Lr34, which belongs to the group of genes that provide partial resistance in the phase of adult plants, is found in the following varieties: Kryzhynka, Vesta, Snizhana, Volodarka, Demetra, Vdiachna, Pamiati Remesla, and Sviatkova (Kozub et al., 2017; Pirko et al., 2012). Eight varieties exhibit polymorphism for the gen Lr34 – Illichivka, Myronivska 30, Myronivska 32, Myronivska 65, Myronivska 66, Pyvna, Ekonomka, Lehenda Myronivska. Perhaps a small frequency of the dominant allele of the Lr34 gene in the varieties of MIW is related to the difficulty of identifying it in field conditions in the Right-Bank Forest-Steppe zone of Ukraine with the use of classical breeding methods, since for varieties of the Plant Breeding and Genetics Institute – National Center of Seed and Cultivar Investigation of the National Academy of Agricultural Sciences of Ukraine frequency is much higher. The varieties Zolotokolosa and Podolianka also contain the gene Lr34 according to (Radchenko and Tishchenko 2010) and (Krattinger et al. 2016).

We found that among the 15 newly created varieties, only 3 varieties – Berehynia myronivska, MIP Dniprianka, and Balada myronivska contain the Lr34 allele (+), which is only 20% of the investigated varieties according to the PCR results, using the caSNP12 marker (Table 2).

It has been established that effective against the pathogen of leaf rust the are genes: Lr9, Lr19, Lr37, Lr42+Lr24, Lr43 (Lr21+Lr39) +Lr24, Lr9+L26, Lr10+Lr24. The genes Lr13, Lr34, Lr37 in combination with other genes, provide the long-term protection of wheat against leaf rust.

The wheat-rye translocation 1BL/1RS was identified in the following varieties: Myronivska 61, Myronivska 27, Mirleben, Myronivska 28, Myronivska 30, Myronivska 31, Myronivska 33, Myrych, Myronivska 65, Myronivska 66, Kryzhynka, Myronivska 67, Vesta, Snizhana, Pereiaslavka, Demetra, Favorytka, Pyvna, Kalynova, Kolos Myronivschyny, Monotyp, Ekonomka, Myronivska storichna, Lehenda Myronivska.

The availability of wheat-rye translocation 1AL/1RS was found in varieties: Kolumbiia, Smuhlianka, Vesnianka, Zolotokolosa, Yasnohirka, Slavna, Yavoryna.

The Lr34 (+) allele is presented in varieties: Kryzhynka, Vesta, Snizhana, Volodarka, Demetra, Vdiachna, Pamiati Remesla, Sviatkova, Podolianka, Zolotokolosa, Berehynia myronivska, MIP Dniprianka, and Balada myronivska according to the results of the research. As a result of research, it was found that the wheat variety Myronivska Ukrainian selection is quite productive in comparison with other varieties and resistant to pathogens of various diseases, especially to the pathogen (brown rust).