Prevalence and diversity of yellow dwarf virus strains in Nebraska cereal crops

Yellow dwarf viruses (YDV), comprising strains of barley yellow dwarf virus (BYDV) and cereal yellow dwarf virus (CYDV), cause economically important diseases in cereal crops in the United States. Although YDV are widespread in Nebraska, information on species distribution and their temporal variability is limited. A statewide survey was conducted during the 2023 and 2024 growing seasons to characterize YDV strain diversity and associated aphid vectors in cereal crops. Total RNA was extracted from symptomatic leaf samples collected from commercial and experimental fields, and viral detection was performed using a multiplex one-step reverse transcription polymerase chain reaction (RT-PCR). Aphid abundance was assessed separately using Berlese funnel from the field-collected plant materials, and species were determined morphologically. In 2023, 68.1% (644/946) of the tested samples were positive for at least one YDV strain, whereas in 2024, only 25.5% (144/564) of the samples tested positive. BYDV-SGV was the predominant strain in 2023, particularly in oats and wheat, whereas SGV+MAV and RPV+SGV strains were the most common coinfections. In contrast, CYDV-RPV and BYDV-MAV predominated in wheat and barley in 2024, whereas PAV was most frequently detected in oats. The bird cherry-oat aphid (Rhopalosiphum padi) was the most abundant aphid species across all crops and locations. These results demonstrate substantial year-to-year variation in the composition of YDV strains in Nebraska cereal crops and confirm the utility of multiplex RT-PCR for field diagnosis. Furthermore, the observed patterns of virus prevalence and aphid abundance emphasize the epidemiological relevance of these findings and support the role of aphid vectors in shaping strain distribution and composition.