Effects of Barley Yellow Dwarf Virus on Growth and Yield of Small Grains in Montana. D. J. Yount, Former Graduate Research Assistant, Department of Plant Pathology, Montana State University, Bozeman 59717. J. M. Martin, Associate Professor, Department of Plant and Soil Science, and T. W. Carroll, Professor, and S. K. Zaske, Laboratory Technician, Department of Plant Pathology, Montana State University, Bozeman 59717. Plant Dis. 69:487-491. Accepted for publication 17 December 1984. Copyright 1985 The American Phytopathological Society. DOI: 10.1094/PD-69-487.

Replicated field trials were conducted to determine the effects of barley yellow dwarf virus (BYDV) on the growth and yield of small grains in Montana. A vector-nonspecific isolate (MT-PAV) of the virus was used to infect six cultivars each of spring barley and spring wheat and five cultivars of winter wheat. Fifteen of these cultivars represented those commercially seeded to most of the wheat and barley acreage in central Montana from 1978 to 1981. One cultivar of spring barley (Sutter) and another of spring wheat (Anza), each previously reported resistant to the disease caused by BYDV, were included for comparison. Rhopalosiphum padi served as the aphid vector species for the inoculation trials. MT-PAV was highly virulent in all Montana small grains tested. On the basis of symptom expression, growth characteristics, and yield factors, all Montana small-grain cultivars were classified as susceptible to the virus disease and intolerant (sensitive) to the virus. When infected plants were compared with uninoculated control plants, the mean reduction in grain yield for the susceptible Montana cultivars was 44.7% for two-rowed barleys, 65.1% for six-rowed barleys, 74.5% for spring wheats, and 67.1% for winter wheats. The mean reduction in 1,000-seed weight was 35.2% for two-rowed barleys, 28.5% for six-rowed barleys, 40.4% for spring wheats, and only 9.6% for winter wheats.