Comparison of nucleic acid hybridisation and other tests for detecting tobacco rattle virus in narcissus plants and potato tubers

Abstract

SUMMARYAll isolates of tobacco rattle virus (TRV) found in naturally infected narcissus leaves produced nucleoprotein particles, mostly in large concentrations but, because of antigenic diversity, less than half of the isolates were identified by immunosorbent electron microscopy (ISEM) and still fewer by enzyme‐linked immunosorbent assay. All were identified by a nucleic acid hybridisation test in which DNA complementary to RNA‐1 of strain PRN of TRV was allowed to react with nucleic acid extracted from leaf tissue.Spraing‐affected tubers in some potato stocks yielded only NM isolates of TRV. These isolates do not produce virus particles and they were therefore not detected by ISEM. The infectivity of nucleic acid extracts from recently harvested tubers with spraing symptoms was much greater than that of extracts prepared from tubers after 8 months' storage. In other potato stocks, some spraing‐affected tubers contained NM isolates and the rest contained particle‐producing isolates (M isolates) of TRV. The infectivity of sap and of nucleic acid, extracted 7 months after harvest from tubers infected with M isolates, was much greater than that of nucleic acid extracted from comparable tubers infected with NM isolates. TRV was detected by nucleic acid hybridisation in extracts of almost all tubers containing either M or NM isolates, even when the tubers were not tested until 7–8 months after harvest. The probable sequence of events occurring after tubers are infected with TRV is outlined, and it is suggested that the virus will rarely become established in fields as a result of planting infected tubers.