ISHS Acta Horticulturae 234: VII International Symposium on Virus Diseases of Ornamental Plants
AN APPRAISAL OF THE IDENTITIES OF POTYVIRUSES INFECTING NARCISSUS |
| Authors: | W.P. Mowat, G.H. Duncan, S. Dawson |
| Abstract:
Among the important virological problems in narcissus are the detection and identification of viruses with potyvirus-like particles, which occur commonly, often in low concentration, in plants of many important cultivars. Four potyviruses are reported to infect narcissus in Western Europe, each associated with, and named after, a distinct disease: narcissus degeneration, narcissus late season yellows, narcissus white streak and narcissus yellow stripe. None of these putative potyviruses has been cultured in experimental hosts. Thus the only available virus sources are naturally infected narcissus plants, which are frequently infected with other viruses. This has hindered the characterisation of the viruses and there has been no good evidence to show that they are single and distinct entities. Apparently pure sources of narcissus late season yellows virus (NLSYV) were obtained by selecting naturally infected plants of cv. Golden Harvest with late season yellows symptoms and containing only potyvirus particles. The virus induced typical symptoms of late season yellows when transmitted by Myzus persicae to virus-tested narcissus plants. Tests with antisera produced to NLSYV showed that it is widespread in commercial plantings, apparently infecting all plants of some cultivars, and is often latent. Therefore the potyvirus particles detected in plants affected by other virus diseases may have been those of NLSYV. In immunoelectron microscopy tests only potyvirus particles reacting with NLSYV antibodies were found in NLSYV-infected plants showing white streak symptoms and thus the cause of the symptoms remains unclear. In contrast when leaf extracts of cv. Grand Soleil d'Or were reacted with antibodies to NLSYV, some of the potyvirus particles present became fully coated with antibodies, some were uncoated and a few were coated for part of their length, indicating that these plants contained a second and distinct type of potyvirus particle, presumably that of narcissus degeneration virus. The association of potyvirus-like particles with yellow stripe disease was less evident. For example, plants of the NLSYV-immune cv. Carlton affected by yellow stripe, whether infected naturally or experimentally by aphid inoculation of virus-tested plants, all contained narcissus latent carlavirus but no potyvirus particles were found. However, cytoplasmic inclusion bodies of the "pseudopinwheel" type were found in thin sections of such plants indicating that a | |
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