On the causal viruses of tomato streak diseases in Japan

Abstract

1. In a survey to determine the causal viruses of tomato streak, 37 collections of streak diseased tomato plants have been examined by inoculating with carborundum to a series of differential hosts. Of these collections, 25 samples (67 per cent) yielded tobacco mosaic virus (TMV), while 9 samples (24 per cent) yielded TMV combined with cucumber mosaic virus (CMV). Potato X virus (PXV) combined with either TMV or CMV, and CMV singly were isolated from 1 sample each.2. Of the 25 samples which yielded TMV, 14 samples produced streak disease on tomato plants, and 11 samples produced only mosaic disease without necrosis, under the experimental conditions. The viruses contained in the former 14 samples caused local lesions on tobacco, while the viruses contained in the latter 11 samples were found to consist of 2 strains: one causes local lesions on tobacco, while the other is considered to be identical with ordinary TMV, not causing local lesions on tobacco. Streak diseases were produced on tomatoes by inoculation with TMV combined with CMV, PXV combined with TMV, or PXV combined with CMV, but inoculation to tomatoes with CMV alone, even in the particular CMV isolate obtained singly from a streak diseased tomato plant, resulted in the development of mosaic symptoms only.3. The virus causing local lesions on tobacco was identical with the tomato streak strain of TMV (Ainsworth (1933), Smith (1957)), Marmor tabaci var. canadense (Holmes (1948)), judged from the results of experiments on host range, the mode of transmissions, physical properties, protective inoculation tests with ordinary TMV, and aggulutination reaction on slides with antiserum of ordinary TMV.4. The symptoms caused singly by the virus of the streak strain of TMV were more severe than the symptoms caused by combined TMV and CMV. The symptoms caused by the streak strain consisted of necrotic streaks on stems, leaves and fruit, while the symptoms caused by the combined TMV and CMV consisted of small necrotic lesions on leaves without necrotic streaks on stems and fruit, in many cases being accompanied with severe mosaic, malformation, fern-leaf appearance of upper leaves, and bushy habit of the plant.