Abstract
Radish yellow edge virus (RYEV), a seed-borne small spherical virus, was newly recognized in young seedlings of Japanese radish (Raphanus sativus L.). RYEV particles of about 30nm in diameter were detected in negatively stained dip preparations from infected seedlings, but a few in number. RYEV was transmitted through seed, and the virus was detected in 80-100% of young seedlings from seeds of all the six cultivars examined. RYEV-infected seedlings usually showed no symptoms, but sometimes showed mild symptoms of yellow edge and dwarfing in their lower leaves. The virus was not transmitted by sap inoculation to Japanese radish, turnip, cabbage, tobacco (cv. Samsun), Chenopodium amaranticolor, C. quinoa, and Gomphrena globosa. The virus was purified by chloroform clarification and three cycles of differential centrifugation followed by sucrose density gradient centrifugation. The purified preparation showed an UV absorption spectrum characteristic of a nucleoprotein. The sedimentation coefficient of the virus measured by analytical centrifugation was about 118S. In thin sections of RYEV-infected leaves, virus particles were observed only in cells of vascular bundles. Inclusion bodies (viroplasms) containing RYEV particles were observed in the cytoplasm of phloem parenchyma cells. Virus particles were observed inside and outside the viroplasms. Phloem necrosis could not be found. Small aggregates of virus particles were also observed in the cytoplasm and plasmo-desmata of phloem parenchyma cells, and in xylem vessels. Virus particles similar to those of RYEV were detected in apparently healthy seedlings from seeds of carrot, spinach, leaf beet (Beta vulgaris var. cicla) and table beet (B. vulgaris var. esculenta cv. Detroit Dark Red).
