Comparative Characterization of Two Luteoviruses: Beet Western Yellows Virus and Barley Yellow Dwarf Virus

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Abstract
A legume isolate of beet western yellows virus (BWYV-CA) and a vector nonspecific isolate of barley yellow dwarf virus (BYDV-PAV-IL) were characterized. An associated top component (BWYV-CA-TC) was isolated with BWYV-CA. BWYV-CA-TC had a maximum absorbance at 275 nm, an S20,w of 62 S, buoyant densities of 1.31 g/ml in CsCl and 1.28 g/ml in C2SO4. No nucleic acid was detected in BWYV-CA-TC and the particles were not infectious. BWYV-CA had a maximum absorbance at 259 nm, an S20,w of 114 S, and buoyant densities of 1.42 g/ml in CsCl and 1.36 g/ml in C2SO4 BYDV-PAV-IL had a maximum absorbance at 258 nm, an S20,w of 106 S, and buoyant densities of 1.41 g/ml in CsCl and 1.35 g/ml in Cs2SO4. The relative molecular masses (Mr) of the major proteins of BWYV-CA-TC, BWYV-CA, and BYDV-PAV-IL were 24,000, 24,000, and 22,500, respectively. The Mr of the undenatured RNA species of BWYV-CA was 1.90 .times. 106 and of BYDV-PAV-IL was 1.85 .times. 106. In negatively stained preparations of purified particles from sucrose density gradients, particle diameters of BWYV-CA-TC, BWYV-CA, and BYDV-PAV-IL were 23 .+-. 2, 25 .+-. 1, and 25 .+-. 1 nm, respectively.