COMPARATIVE HOST RANGES OF SIX PLANT VIRUSES

Abstract

THE FAILURE of viruses to multiply except within living cells has led to considerable speculation regarding the essential materials or conditions necessary for their reproduction. Holmes (23) recently approached the problem from the standpoint of the taxonomic affinities of plant species found to be susceptible or insusceptible to tobacco-mosaic virus (Marmor tabaci H.).2 He found that classification of tested species of plants into four groups according to their natural relationships revealed a group consisting of only susceptible species, a group of largely susceptible species, a group made up of about half susceptible and half insusceptible species, and a group of mostly insusceptible species. Holmes suggested that there may be an orderly distribution in nature of substances or conditions necessary for multiplication of the virus. If this interpretation is correct, other plant viruses might show a similar tvpe of host distribution. A comparison of the host ranges of several plant viruses might lead to a knowledge of certain differences and similarities in specific chemical or physical properties required bv viruses for reproduction. With this idea in mind, plants belonging in a large number of families have been tested for susceptibility to six different viruses. The results of the tests are presented herewith. MATERIALS AND METHODS.-Virus stocks.-The following plant viruses were used: Tobacco-necrosis virus (Marmor lethale H.). Cucumber-mosaic virus (M. cucumeris H. var. vulgare H., judicis H., and vignae H.); most tests were made with the ordinary strain, vulgare. Cucurbit-mosaic virus (M. astrictum H. var. aucuba H.). Alfalfa-mosaic virus (M. medicaginis H. var. typicum Black and Price). Tobacco-ringspot virus (Annulus tabaci H. var. virginiensis H.). Tomato-ringspot virus (A. zonatus H.). The table to be considered presently includes results of other workers with additional virus strains. Most of these strains are listed in the Handbook of Phytopathogenic Viruses (24). One strain not listed there but included in the table is the potato-calico strain of alfalfa-mosaic virus (Marmor medicaginis var. solani Black and Price), only recently shown to belong in the alfalfa-mosaic virus group (7). The virus stocks were transferred to young plants at frequent intervals in order to insure a high virus content in the juices to be used as inoculum. Cucumber (Cucumis sativus L.) served as a source plant for cucurbit-mosaic virus, Turkish tobacco (Nicotiana tabacum L.) as a source plant for the other