Wheat dwarf virus in Ukraine: occurrence, molecular characterization and impact on the yield

Wheat dwarf virus (WDV) causes one of the most serious cereal diseases in many countries. In spring 2020, we observed wheat plants with symptoms of severe dwarfism, no heading/reduced heading, leaf streaking and yellowing in five regions located in western, central and northern parts of Ukraine. The aim of the study was to identify the virus causing mentioned symptoms, investigate its impact on wheat yield and perform phylogenetic analysis of the detected viral isolates. Using double-antibody sandwich enzyme-linked immunosorbent assay (DAS-ELISA) and polymerase chain reaction, WDV was confirmed in 14 varieties of winter and spring wheat. CP gene regions of two WDV isolates were sequenced: Khm-K-Ukr, MW176036 (from winter wheat var. Kolonia, Khmelnytskyi region) and MIP-12-Ukr, MW176037 (winter wheat D-12-1, Kyiv region). Phylogenetic analysis showed that Khm-K-Ukr and MIP-12-Ukr belong to the clade E. These isolates have the highest level of sequence identity with the barley isolate WDV-Lip from Poland (KY781940), the Ukrainian wheat isolate WDV-Uk-Miron (FN806784) and the isolate from Estonia (MK193742) and clustered on the same branch indicating their possible common origin. The isolate MIP-12-Ukr has 1 unique aa substitution and Khm-K-Ukr has 4 aa mutations in the studied CP gene region in comparison with other 52 WDVs from GenBank. It was found that WDV significantly reduced the number of seeds per spike 2.6–3.4 -fold, the weight of seeds per spike (3.8–4.2-fold), while weight of 1000 grains was also decreased (by 2.6–3.5 times). These results indicate that WDV is a big threat to wheat crops in Ukraine.