Studies on the virus of turnip yellow mosaic

Abstract

A new virus affecting cruciferous plants is described and the name suggested for it is theturnip yellow mosaic virus.The virus is sap-transmissible and has a dilution end-point in extracted sap of 10−5. The thermal inactivation point lies between 70 and 75° C.The virus is not transmitted by insects with sucking mouthparts, but the insect vector in nature is a flea-beetle,Phyllotretasp. More than one species of flea-beetle can transmit the virus.Under experimental conditions the virus has been transmitted by the mustard beetle,Phaedon cochleariaeand its larva; by the ‘long-horn’ grasshopper,Leptophyes punctatissimaBosc.; by the ‘short-horn’ grasshopper,Stauroderus bicolorCharp. and by the common earwig,Forflcula auriculariaLinn. Lepidopterous larvae have, so far, failed to transmit the virus.The relationship of the virus with biting insects is discussed.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.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.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.The nucleic acid-free material does not seem to be infectious.