Studies on the virus of turnip yellow mosaic

<jats:p>A new virus affecting cruciferous plants is described and the name suggested for it is the<jats:italic>turnip yellow mosaic virus.</jats:italic>The virus is sap-transmissible and has a dilution end-point in extracted sap of 10<jats:sup>−5</jats:sup>. The thermal inactivation point lies between 70 and 75° C.</jats:p><jats:p>The virus is not transmitted by insects with sucking mouthparts, but the insect vector in nature is a flea-beetle,<jats:italic>Phyllotreta</jats:italic>sp. More than one species of flea-beetle can transmit the virus.</jats:p><jats:p>Under experimental conditions the virus has been transmitted by the mustard beetle,<jats:italic>Phaedon cochleariae</jats:italic>and its larva; by the ‘long-horn’ grasshopper,<jats:italic>Leptophyes punctatissima</jats:italic>Bosc.; by the ‘short-horn’ grasshopper,<jats:italic>Stauroderus bicolor</jats:italic>Charp. and by the common earwig,<jats:italic>Forflcula auricularia</jats:italic>Linn. Lepidopterous larvae have, so far, failed to transmit the virus.</jats:p><jats:p>The relationship of the virus with biting insects is discussed.</jats:p><jats:p>Turnip yellow mosaic virus has been obtained from several cruciferous plants as a nucleoprotein of the pentose type. It crystallizes from salt solutions as isotropic octahedra and from 20% alcohol at pH 3·7 as birefringent needles. On centrifuging out of solution the pellets are also crystalline. The virus preparation contains some 22% of nucleic acid.</jats:p><jats:p>The virus is denatured at room temperature in alcohol of concentration greater than 30% in neutral solutions, and the nucleic acid, which is a large polymerized particle, is liberated.</jats:p><jats:p>The preparations have been found to consist of 80 % of a nucleoprotein and 20 % of a nucleic acid-free protein which may be isolated by high-speed centrifuging. The latter has the same electrophoretic mobility and isoelectric point (pH 3·7) as the nucleoprotein; both crystallize in the same crystal form, and they are serologically identical.</jats:p><jats:p>The nucleic acid-free material does not seem to be infectious.</jats:p>