PROPERTIES OF COCKSFOOT STREAK AND COCKSFOOT CRYPTIC, 2 VIRUSES INFECTING COCKSFOOT (DACTYLIS-GLOMERATA) IN SCOTLAND

A Scottish isolate of cocksfoot streak virus (CSV-S) was found to have flexuous filamentous particles which, in sap of infected cocksfoot pl ants, had a modal length of 712 nm. It was transmitted from infected t o healthy cocksfoot plants in a non-persistent manner by Myzus persica e and by mechanical inoculation of infective sap extracts containing a n anti-oxidant. Apart from cocksfoot, mechanical inoculation of infect ive sap succeeded in infecting only four of 22 plant species tested. T he infectivity of sap extracts containing 0.2% thioglycerol was lost a fter heating for 10 min at 55-degrees-C but not 50-degrees-C, storage at room temperature for 48 but not 24 hours, and after diluting 10(-2) to 10(-3). Highly purified preparations of CSV-S particles sedimented as a single component with a sedimentation coefficient of 139S and ha d a buoyant density in rubidium bromide of 1.31 g/cm3. Virus particles were composed of one protein and one ssRNA species with estimated M(r ) of 31 000 and 3.2 x 10(6) respectively. In ELISA, an antiserum prepa red to CSV-S detected the virus in all aerial parts of infected cocksf oot plants and, when present in the ratio of 1 infected leaf : 1000 he althy leaves. Both CSV-S-infected and -uninfected cocksfoot also conta ined a previously undescribed virus with isometric particles c. 30 nm in diameter. This virus, named cocksfoot cryptic virus (CCV), was seed -borne in two cvs of cocksfoot tested and its particles contained two dsRNA species of estimated M(r) of 1.14 x 10(6) and 1.27 x 10(6). Desp ite the fact that particles of CSV-S were largely free from CCV partic les following exclusion chromatography on agarose beads prior to immun isation, immunoelectron microscopy (IEM) showed that the antiserum pre pared to CSV-S also contained some antibodies to CCV. Evidence from IE M suggested a possible distant serological relationship of CCV to ryeg rass and beet (BCV 1 or BCV 2, or both) cryptoviruses, all members of sub-group A of cryptoviruses.