Abstract
Barley yellow mosaic virus (BYMV) and wheat yellow mosaic virus (WYMV) were purified from diseased barley and wheat by clarification with carbon tetrachloride, followed by differential centrifugation and sucrose density gradient centrifugation. Further purification was carried out by isopycnic gradient centrifugation in cesium chloride. The viruses were well dissolved by citrate buffer (0.1M, pH 7.0), but were not dissolved or aggregated by phosphate buffer (0.1M, pH 7.0), borate buffer (0.005M, pH 9.0), acetate buffer (0.1M, pH 5.0), or citrate buffer (0.01M, pH 7.0). The viruses were resistant to carbon tetrachloride, but susceptible to chloroform and butanol. Under sucrose density gradient centrifugation, two zones occurred in the tube. The top zone consisted mainly of short particles, and the bottom zone of short and long particles. Buoyant densities of BYMV and WYMV were 1.294 and 1.281g/cm3, respectively. The ultraviolet absorption spectra of the viruses were typical for nucleoproteins. The characteristic shoulder was present at 290nm in both viruses. The corrected 280:260 ratios of the viruses were 0.88, indicating presence of 5% nucleic acid. The infectivity of the partially purified preparations was rather low. However, an increase in infectivity was obtained with the addition of healthy plant sap. Infectivities of the bottom zone, and mixtures of two zones, were high, but that of the top zone only was low. The viruses purified by isopycnic gradient centrifugation were infectious. Particle length distributions of partially purified preparations had two broad peaks at 200-300nm, and 600nm, whereas three peaks at 275-300nm, and 530-560nm, and 770-820nm were observed in leaf-dip preparations. BYMV and WYMV antisera, both having a homologous titer of 1/640 in a complement fixation test after absorption with normal plant component, were obtained from rabbits which had been immunized with the viruses purified by sucrose density gradient centrifugation. There was antigen common to BYMV, WYMV, and rice necrosis mosaic virus, but each of these also seemed to have its own specific antigen. The antisera did not react with soil-borne wheat mosaic virus.
