Prevalence of wheat streak mosaic rymovirus (Tritimovirus tritici) on wheat in the Russian Federation and genetic characteristics of identified isolates

Wheat is the leading agricultural crop and is widely cultivated in the Russian Federation. One of the most harmful pathogens of this crop is the wheat streak mosaic rymovirus ( Tritimovirus tritici , Wheat streak mosaic rymovirus, WSMV), which can cause significant yield losses, reaching 100 %. The purpose of the current study was to determine the prevalence of WSMV in wheat crops in different regions of the Russian Federation and to analyze the genetic characteristics of isolates of this virus identified in the Krasnodar Territory. Identification of WSMV in selected wheat samples was carried out by the ELISA method with test systems from leading manufacturers and by the PCR method with species-specific primers. The obtained amplification products were sequenced. The results of the study conducted in 2024 showed a wide prevalence of WSMV in several constituent entities of the Russian Federation, which was not established in 2021–2023. The incidence of this virus in samples from the Stavropol Territory, Krasnodar Territory, the Republic of Crimea and the Volgograd Region was 100 %, 45.4 %, 41.7 and 30.4 %, respectively. There has been established a dominant distribution of isolates of this virus belonging to the WSMV-B strain in the Krasnodar Territory. According to the nucleotide sequence in the 6K1 and CI genes, most of these isolates are characterized by high identity with a fairly narrow group of isolates of the WSMV-B strain distributed in Austria, Germany, Poland, Ukraine, Turkey, the Czech Republic, France, and the USA. The highest identity was determined for isolates S34Edirne from Turkey, DSMZ PV-0356 from Ukraine and Sze from Poland, i.e. from countries located fairly close to the borders of the Russian Federation. There were also identified two WSMV isolates with a higher identity to the WSMV-D strain than to the WSMV-B strain. The presence of a sufficiently high genetic variability in the identified isolates indicated repeated cases of WSMV invasion into the Krasnodar Territory from several independent sources.