First report of Triticum mosaic virus infecting oat crop in the United States

Authors: BARMAN, MRITUNJOY - University Of Nebraska; DAVIS, THOMAS - University Of Nebraska; HEIN, GARY - University Of Nebraska; Tatineni, Satyanarayana - Ts; MONDAL, SHAONPIUS - University Of Nebraska

Submitted to: Plant Disease
Publication Type: Research Notes
Publication Acceptance Date: 6/4/2024
Publication Date: 7/29/2024
Citation: Barman, M., Davis, T.W., Hein, G.L., Tatineni, S., Mondal, S. 2024. First report of Triticum mosaic virus infecting oat crop in the United States. Plant Disease. 108(8). https://doi.org/10.1094/PDIS-04-24-0754-PDN.
DOI: https://doi.org/10.1094/PDIS-04-24-0754-PDN

Interpretive Summary: Triticum mosaic virus (TriMV) is one of the economically important wheat curl mite-transmitted viruses infecting wheat in the Great Plains region. Except for wheat, it is not known whether TriMV can infect other cereal crops in Nebraska. During the 2023 growing season, oat field surveys were conducted in Nebraska to determine the presence of viruses, and it was found that several symptomatic oat plants from growers’ fields were positive for TriMV. This is the first report of TriMV infecting oats in growers’ fields and warrants thorough field surveys for potential TriMV infection on other cereal crops in the Great Plains region.

Technical Abstract: Triticum mosaic virus (TriMV, genus Poacevirus, family Potyviridae) was first reported in 2006 to infect wheat, and since then, it has been established as a constraint for US wheat production. In the field, TriMV often exists as a coinfection with wheat streak mosaic virus (WSMV), and these two viruses interact synergistically to produce severe symptoms and greater yield loss. Both TriMV and WSMV are transmitted by wheat curl mites (Aceria tosichella Keifer). Though wheat is the primary host reported for TriMV in the field, TriMV can infect oat, rye, barley, and several other cereals and grasses as hosts under experimental conditions. However, there are no documented cases of TriMV infecting oats in the field. During the 2023 growing season, a total of 273 field oat plants showing foliar yellowing, yellow flecking, and streaking symptoms were collected from four different fields in Nebraska. Reverse transcription-polymerase chain reaction (RT-PCR) from field-collected oat samples revealed that out of 273 symptomatic samples, 254 (93.04%) tested positive for TriMV or WSMV. Out of the total positive samples, 238 were positive for WSMV (93.70 %), 12 plants tested positive for both TriMV and WSMV (4.70%), and 4 plants were infected with TriMV alone (1.60%). As a secondary confirmation, the gel-purified RT-PCR fragments were sequenced, and it was found that the coat protein (CP) gene showed >98% identity to the corresponding sequences of reported TriMV isolates. For further validation, virus inoculum was prepared by grinding field-collected plant material from plants with only TriMV present in 20 mM sodium phosphate buffer, pH 7.0, and then mechanically inoculating two-week-old oats (cv. Shaw n=8) and wheat (cv. Sattler, n=8) plants. Three weeks post-inoculation, all eight wheat plants exhibited mild yellowing and streaking symptoms, while oat plants did not show foliar symptoms. All wheat and oat plants were further assayed with DAC-ELISA using antibodies produced against TriMV CP. The specific attribution of these symptoms to TriMV in oats is not possible as none produced prominent symptoms, which could be due to oat cultivar differences. To our knowledge, this is the first report of TriMV infection in US oat fields. Our finding highlights the imperative need for thorough inquiries into the incidence and impact of the virus in other crops besides wheat and its economic impact on their cultivation.