The cross‐reactivity of two polyclonal antisera with various members of the Potyviridae was determined using four different serological methods. An antiserum (no. 314) prepared against apparently intact turnip mosaic potyvirus (TuMV) particles showed a high cross‐reactivity with all of 20 aphid‐borne potyviruses tested as well as the mite‐borne ryegrass mosaic rymovirus (RGMV) and the fungus‐borne barley mild mosaic bymovirus (BaMMV) with two of the four methods used (indirect PTA‐ELISA or IEM and Western blotting). In immunoelectron microscopic decoration, about two thirds of the viruses tested reacted positively whereas in the direct DAS‐ELISA only the homologous TuMV reacted positively.
Another antiserum (no. 203) produced by using as immunogen a mixture of the dissociated core proteins of three trypsin‐treated potyviruses (potato A and V and plum pox viruses), reacted positively in both indirect ELISA and Western blotting with all aphid‐borne potyviruses and RGMV. No reactions were obtained with the other two methods. The causes for these different reactivities are discussed. Both antisera are useful for the detection of aphid‐borne potyviruses, but one (no. 314) is especially suitable for the detection of these viruses under routine conditions by use of a simple indirect PTA‐ELISA.
ln attempts to use cross-reacting antibodies for the broad-spectrum detection of potyviruses, two broad-spectrum immunoreagents, the monoclonal antibody P-.^-3H8 and antiserum TuMV-3I4raised against an isolate of peanut stripe virus and turnip mosaic virus, respectively, were examined for their ability to detect members of the Polyriridae in a simple indirect plate-trapped antigen (PTA) ELISA. Both immunoreagents reacted strongly not only wilh isolates of 50 different virus species of the genus Posyrirux but also with several isolates of ryegrass mosaic virus, the type member of the genus Ryinovirm. A few members of the genus Po!yvirus as well as agropyron mosaic and hordeum mosaic viruses, two other species of the genus Rymoviru.s. did not react with P-3-1H8 but only with TuMV-314 which showed the highest degree of cross-reactivity. In no case were positive reactions obtained with nnembers of the genera Byniovints and fpontorirus. These two immunoreagents which appear to be directed to conserved epitopes gave good results when they were employed for detecting potyviruses m field samples from ornamental (Liliales) and leguminous plants. The potential and limitations of cross-reactive antibodies for the routine detection of potyviruses are discussed.
Resistance tests of 127 parsley accessions (Petroselinum crispum) were carried out during 2 years of field investigations involving natural infection for black leaf spot (Alternaria radicina), mildew (Erysiphe heraclei), leaf chlorosis (Fusarium oxysporum) and viruses, particularly celery mosaic virus (CeMV). In this first extensive evaluation of parsley for all tested pathogens accessions were found to be free of symptoms.Varieties of vars. crispum and tuberosum contained more accessions weakly infected or immune to black leaf spot than vars. vulgare and neapolitanicum. In a separate test five var. crispum accessions showed significantly reduced disease ratings, indicating their potential as sources of resistance. Mildew attacked almost the same number of accessions in both years: 29 accessions of var. crispum showed no symptoms, but 16 of the var. tuberosum accessions were highly susceptible. Whereas in the var. vulgare one half of the introductions were moderately or strongly infected by viruses, mainly CeMV, a high number of plants remained uninfected in the vars. crispum, neapolitanicum and tuberosum. In the case of F. oxysporum, the greatest amount of infection was in the var. crispum during both years. The sources of resistance described including multiple resistance would be of interest in future breeding programmes for resistance to the parsley pathogens discussed.
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