Über die Korrelation zwischen Partikellänge und Infektiosität beim Vergilbungsvirus der Rüben

Abstract

Crude leaf sap of plants suffering from sugar beet yellows was partially purified by density gradient centrifugation in the cold at different values of pʜ (6,2-9,0). After standing over night at 2° C the material was dialysed against buffer of pʜ 6,8 at room temperature. - As estimated by electron microscopy the most frequent length of the threadlike particles (Fig. 2) which were believed to be the infectious agent of sugar beet yellows shows a gradual shift from longer to shorter ones with rising pʜ (Fig. 1 a-e). The infectivity of the suspensions depends upon the pʜ of the preparation too. From the distribution curve of the particle lengths the relative concentrations of particles with different given minimal lengths were estimated. The dependence from the pʜ of the preparation of these relative concentrations was compared with that of the infectivity. Best agreement was observed with particles of 12 700 - 12 800 A minimal length (Fig. 3). This length seems to be identical with the “normal length” of the particles found in exsudates (12 400 -12 500 A). From these results it was concluded that a) particles which possess the normal length as found in exsudates are the infective entities of this disease, b) shorter particles are non-infectious, c) the infectious entities of the sugar beet yellows virus are of the threadlike type. There is no evidence that spherical particles are necessary for starting an infection with the sugar beet yellows virus.