Resistance to Beet Western Yellows Virus Among Forage Brassicas. P. E. Thomas, Research Plant Pathologist, USDA-ARS, Washington State University, Irrigated Agriculture Research and Extension Center, Prosser 99350-9687. D. W. Evans, L. Fox, and K. D. Biever. Agronomist, Washington State University, Irrigated Agriculture Research and Extension Center, Prosser 99350-9687; Biological Technician, and Research Entomologist, USDA-ARS, Yakima Agricultural Research Laboratory, Yakima, WA 98902. Plant Dis. 74:327-330. Accepted for publication 7 November 1989. This article is in the public domain and not copyrightable. It may be freely reprinted with customary crediting of the source. The American Phytopathological Society, 1990. DOI: 10.1094/PD-74-0327.

Fourteen forage Brassica cultivars representing four species were evaluated for resistance to beet western yellows virus (BWYV), potato leafroll virus (PLRV), and the tomato yellow top strain of PLRV (PLRV-TY) under field exposure. Incidence of field infection with BWYV ranged in several susceptibility classes from less than 2 to 100%. The four most susceptible cultivars were all turnips. The four most resistant cultivars included one each of the four Brassica species. All four species were represented among the intermediately susceptible cultivars. Once infection was achieved, there was little or no difference among the cultivars in resistance to systemic virus accumulation. Symptoms of BWYV were mild. Neither strain of PLRV was detected by ELISA or aphid transmission. There was no correlation between numbers of aphids on plants in the fall and susceptibility to infection. All Brassica cultivars survived winters, but neither live aphids (Myzus persicae) nor aphid eggs were found on plants at the end of winter.