RESUMEN
Common winter wheat is the main grain crop cultivated in the North Caucasus. Rust disease damage is one of the factors limiting wheat productivity. There are three species of rust in the region: leaf (Puccinia triticina), stem (P. graminis) and stripe rust (P. striiformis), and their signif icance varies from year to year. The most common is leaf rust, but in the last decade the frequency of its epiphytotic development has signif icantly decreased. At the same time, an increase in the harmfulness of stripe rust (P. striiformis) is noted. Stem rust in the region is mainly absent or observed at the end of the wheat growing season to a weak degree. Only in some years with favorable weather conditions its mass development is noted on susceptible cultivars. It is believed that the sources of infection with rust species in the North Caucasus are infested soft wheat crops, wild-growing cereals and exodemic infection carried by air currents from adjacent territories. In the North Caucasus, forage and wild grasses are affected by Puccinia species almost every year. Depending on weather conditions, the symptom expression is noted from late September to December and then from late February to May-June. Potentially, an autumn infection on grasses can serve as a source for infection of winter soft wheat cultivars sown in October. The purpose of these studies is to characterize the virulence of P. triticina, P. graminis, P. striiformis on wild cereals and to assess the specialization of causative agents to winter wheat in the North Caucasus. Infectious material represented by leaves with urediniopustules of leaf, stem and stripe rusts was collected from wild cereals (Poa spp., Bromus spp.) in the Krasnodar Territory in October-November 2019. Uredinium material from P. triticina, P. striiformis, and P. graminis was propagated and cloned. Monopustular Puccinia spp. isolates were used for virulence genetics analysis. In experiments to study the specialization of rust species from wild-growing cereals on common wheat, 12 winter cultivars were used (Grom, Tanya, Yuka, Tabor, Bezostaya 100, Yubileynaya 100, Vekha, Vassa, Alekseich, Stan, Gurt, Bagrat). These cultivars are widely cultivated in the North Caucasus region and are characterized by varying degrees of resistance to rust. Additionally, wheat material was inoculated with Krasnodar populations of P. triticina, P. striiformis, P. graminis from common wheat. In the virulence analysis of P. triticina on cereal grasses, four phenotypes (races) were identif ied: MCTKH (30 %), TCTTR (30 %), TNTTR (25 %), MHTKH (15 %), and f ive were identif ied in P. graminis (RKMTF (60 %), TKTTF, RKLTF, QKLTF, LHLPF (10 % each). Among P. striiformis isolates, three phenotypes were identif ied using the International and European sets of differentiating cultivars - 111E231 (88 %), 111E247 (6 %) and 78E199 (6 %). Using isogenic Avocet lines, 3 races were also identif ied, which differed among themselves in virulence to the Yr1, Yr11, Yr18 genes (with the prevalence of virulent ones (94 %)). Composite urediniums' samples (a mixture of all identif ied races) of grass rust of each species were used to inoculate winter wheat cultivars. The most common winter wheat cultivars (75 %) were characterized by a resistant response when infected with P. graminis populations from common wheat and cereal grasses. All these cultivars were developed using donors of the rye translocation 1BL.1RS, in which the Lr26, Sr31, and Yr9 genes are localized. The number of winter wheat cultivars resistant to leaf rust in the seedling phase was lower (58 %). At the same time, all the studied cultivars in the seedling phase were susceptible to P. striiformis to varying degrees. The virulence analysis of the leaf, stem and stripe rust populations did not reveal signif icant differences in the virulence of the pathogens between wild-growing cereals and soft wheat. Urediniomaterial of all studied rust species successfully infested soft wheat cultivars. The results obtained indicate that grasses are rust infection reservoirs for common wheat crops in the North Caucasus.
RESUMEN
In order to prevent crop yield losses from the most dangerous and economically important pathogenic organisms, it is necessary not only to monitor the virulence gene pool, but also to study the nature of pathogen variability and determine the potential for the emergence of new genes and races. This requires centralized collections of fungal cultures characterized by a set of stable strains to provide for phytopathological, immunological, breeding, genetic, toxicological, parasitological and other studies. The State Collection of Phytopathogenic Microorganisms of the ARSRIP is the State Depository of Phytopathogenic microorganisms that are non-pathogenic to humans or farmed animals. Currently, it has more than 4,500 accessions of plant pathogenic strains of fungi, oomycetes, bacteria, viruses, phytoplasmas, and the collection is updated annually. For this purpose, the study of the inter- and intraspecific genetic diversity of genus Fusarium was carried out in agricultural systems of the Krasnodar Territory. In 2020, the State Collection of Phytopathogenic Microorganisms was supplemented with 13 strains of Fusarium fungi isolated from tissues of winter wheat plants collected in several locations of the Krasnodar region. The complex of Fusarium fungi revealed on winter wheat usually included Fusarium oxysporum, F. culmorum, F. lolii, F. graminearum, F. fujikuroi, F. sporotrichioides, etc. The effect of the preceding crop on the frequency of Fusarium species isolated from winter wheat was observed. After series cloning of collected isolates, 21 strains of different fungal species characterized by stable morphology traits and known pathogenic and phytotoxic properties were selected for collection replenishment. Significant differences in pathogenic activity were revealed between fungi belonging to either the same or different species; the manifestation of this activity varied from the absence of any effect of spore suspensions on seedling development to a complete inhibition of their growth. The phytotoxic activity towards wheat seedlings varied from medium to high. Species possessing a high intensity of phytotoxic activities are the most dangerous for wheat, since they promote accumulation of dangerous phytotoxins in plant tissues.