Biological and biochemical properties of an isolate of cherry rasp leaf virus from red raspberry

Abstract

SUMMARYA mechanically transmissible virus obtained from symptomless plants of a red raspberry selection imported into Scotland from Quebec, Canada was indistinguishable serologically from a cherry isolate of cherry rasp leaf virus (CRLV). The raspberry isolate, CRLV‐R, was graft transmitted to several virus indicator species and cultivars of Rubus without inducing noticeable symptoms. In Chenopodium quinoa sap, CRLV‐R lost infectivity after dilution to 10‐5 or heating for 10 min at 60°C but was infective after 16 days (the longest period tested) at 18°, 4° or ‐ 15°C. The virus particles are isometric, c. 28 nm in diameter, and were purified with difficulty from infected C. murale and C. quinoa plants. The particles comprise two nucleoprotein components with sedimentation coefficients of 89 and 115 S and are prone to aggregate during purification. When centrifuged to equilibrium in CS2SO4 solution, purified virus preparations formed two major components with p= 1·28 and 1·36 g/cm3. Virus particles contained two RNA species which, when denatured in glyoxal and electrophoresed in agarose gels, had estimated mol. wt of 2·56 × 106 (RNA‐1) and 1·26 × 106 (RNA–2). Infectivity of CRLV‐R RNA was abolished by treatment with proteinase K, suggesting that the RNA is linked to protein necessary for infectivity; RNA molecules contained polyadenylate. In reticulocyte lysates, CRLV‐R RNA stimulated the incorporation of 3H‐leucine, mainly into two polypeptides of estimated mol. wt 200 000 and 102 000. When electrophoresed in polyacrylamide gels, protein obtained from CRLV‐R particles purified by centrifugation to equilibrium in Cs2SO4 separated into three bands with estimated mol. wt 26 000, 23 000 and 21 000.