Tolerance to Wheat Streak Mosaic Virus in Spring and Winter Wheat Cultivars1

The effects of wheat streak mosaic virus (WSMV) were evaluated on 9 spring wheat (Triticum aestivumL.) cultivars in 1969, 14 spring and 24 winter wheat cultivars in 1970, and 21 winter wheat cultivars in 1971. Plants were mechanically inoculated and the effects measured relative to control plants. Seed yield, plant height, test weight, 1000‐seed weight, and seeds per head were drastically reduced by the virus, whereas percent protein increased. In some instances heads per tiller and plants per plot were decreased slightly. Spring wheat cultivars ‘Chris,’ ‘Bonanza,’ and ‘Fortuna’ and winter wheat cultivars ‘Scout,’ ‘Scout 66,’ ‘Lancer,’ ‘Bronze,’ ‘SD6716,’ ‘SD66171,’ ‘OK6955033,’ ‘NB68508,’ ‘SD6742‐1,’ and ‘Trader’ were found to possess desirable degrees of tolerance to WSMV as measured by both yield of inoculated plants and percent yield reduction as a result of infection. Tolerance shown by these cultivars can make them economically important in areas where the disease is pandemic and useful in breeding programs.