Wheat streak mosaic disease is caused by wheat streak mosaic virus (WSMV) and two other viruses and persistently limits wheat yields in the Great Plains region of the United States. Seed transmission of viruses is an important consideration in international movement and is important epidemiologically. Seed transmission of WSMV in wheat was first reported from Australia in 2005, but there is little data from United States cultivars on the rate of seed transmission. In 2018, mechanically inoculated winter and spring wheat cultivars were evaluated in Montana. We found differences in WSMV seed transmission rates between winter and spring wheat, with average transmission rates in spring wheat (3.1%) being five times higher compared to winter wheat (0.6%). Seed transmission rates in spring wheat were twice as high as the highest previously reported transmission rate for individual genotypes, 1.5%. The results from this study provide a strong argument for increasing the current testing of seed for breeding purposes prior to international movement when WSMV has been observed and caution against using grain from WSMV-infected fields as seed source because it can heighten the risk of wheat streak mosaic outbreaks.
Keywords: mechanical inoculation; seed transmission; spring wheat; wheat streak mosaic virus; winter wheat.