Host range studies with fifty-two plant viruses.
AbstractThe author describes the reactions of 15 plant spp. in families related to the Caryophyllaceae (Hutchinson's classification) when mechanically inoculated at the Plant Pathology Laboratory, Harpenden, with 68 isolates of 52 plant viruses. No general relationship was established between susceptibility to particular viruses and taxonomic relationships of the hosts, some of which were susceptible to many more viruses than others. Chenopodium amaranticolor, Gomphrena globosa, and Tetragonia expansa were hosts for many of the viruses and make suitable standard test plants. Amaranthus caudatus, Celosia argentea, beet, and spinach were of limited use in diagnostic or quantitative work. Dianthus barbatus and Primula malacoides were convenient plants for maintaining stock cultures of some viruses. All 15 spp. contained inhibitors, none of which prevented any of the viruses from infecting the 15 indicator plants, though several spp. contained inhibitors prevent-ing infection of tobacco, Nicotiana glutinosa, Phaseolus vulgaris, and cowpea. In some hosts systemic invasion depended on several apparently independent factors, such as temp., virus conc., virus strain, and type of local lesion.
In many instances, strains of 1 virus had different host ranges or caused different kinds of symptoms, while similar symptoms were sometimes set up by different viruses. Some viruses causing similar symptoms on different test plants also shared other properties; lettuce mosaic and pea mosaic viruses, for example, induced similar and characteristic reactions in Chenopodium, Gomphrena, Amaranthus, and Primula; both possessed similar in vitro properties; both were aphid-transmitted in the non-persistent manner; and both were sometimes seed-borne. Both infected pea and sweet pea, and neither infected Phaseolus vulgaris.
Host-range studies, it is concluded, can be used to separate similar viruses or virus strains and can suggest similarities between viruses, but are unlikely to form a useful basis for a natural classification of viruses.