Potato leafroll virus, its purification from its vector Myzus persicae

Experiments were described on the purification of potato leafroll virus (PLRV) from its vector <em>Myzus persicae.</em> Preliminary experiments demonstrated that much non- viral material had to be removed from aphid macerates to obtain a pure virus preparation. This was achieved by a multistep procedure, in which the aphid macerates were emulsified with chloroform at pH 5.0. The virus present in the interphase between the chloroform and water phases was extracted from the interphase, and concentrated by high-speed centrifuging. The virus suspension obtained was subjected to a phase system of butoxy-ethanol, ethoxy-ethanol and 2.5 M phosphate buffer pH 7.5, and centrifuged in a sucrose density gradient column.<p/>A fairly pure virus preparation was obtained when the material from the infective zone of the gradient was concentrated at 90,000 g for 3 h. Particles with a diameter of 23 mμand with a hexagonal outline were found in each preparation by electron- microscopy. The PLRV isolate purified was free of any contaminating virus when its biological purity was tested. One of the PLRV isolates used in the preliminary experiments, was contaminated with other, presumable persistent, viruses. Their properties and some studies on their host range were described. These viruses were referred to as virus-like particles