Yasuo Komuro

Inoculation experiments of several plant viruses to duck-weed (Spirodela polyrhiza)

Multiplication of ordinary strain of tobacco mosaic virus (TMV) on the duck-weed (Spirodela polyrhiza) was reported in the preceding paper (Komuro and Iwaki 1964). This paper deals with the results of inoculation experiments of several plant viruses and virus strains to the duck-weed.1. Yellow strain and tomato streak strain of TMV, both isolated from tomato in 1963, were also proved to multiply on the duck-weed without symptom as in the case of ordinary strain of TMV.2. On the other hands, cucumber mosaic virus, alfalfa mosaic virus, turnip mosaic virus, and also watermelon mosaic virus were not able to multiply on the same weed even in repeated inoculation experiments.3. Potato virus X (PVX) was ascertained to multiply on the duck-weed from the following experimental results.i) Quantity of PVX recovered from the inoculated duck-weeds on the 3rd day and 5th day after inoculation was small, but it became larger on the 10th and 20th day after inoculation.ii) Vein-clearing sometimes appeared on the fronds of inoculated duck-weed, and the virus was recovered in larger quantities from the fronds showing vein-clearing than from those having no symptoms.iii) Particles, about 500mμ in length, were observed in the juice of fronds inoculated with PVX under an electron microscope, while no such particles were recognized in the juice of healthy fronds.iv) Juice from duck-weed having vein-clearing symptom showed the precipitation reaction when it was mixed with PVX-antiserum.4. Ordinary strain of TMV, and PVX both multiplied on the duck-weed, when these two viruses were inoculated at the same time, and the fronds of duck-weed showed vein-clearing, as in the inoculation with PVX alone.

Recognition of lettuce mosaic virus in Japan

1) In recent years, a mosaic disease of lettuce has been recognized in the vicinity of Tokyo as one of the most destructive diseases of lettuce. Symptoms on crisp-head type varieties, Imperial 847 and Great Lakes, are conspicuous, leaves becoming distorted and frequently developing mosaic or vein-clearing. In butter-head type variety, Wayahead, very faint mosaic or vein-clearing, and in some individuals, necrotic flecks are observed.2) Twenty-three collections of mosaic lettuce plants were tested for the causal viruses by inoculating with carborundum to several indicator plants. As a result, 4 samples yielded cucumber mosaic virus, while the other 19 samples were found to contain a virus hitherto unreported from Japan.3) This virus was readily transmitted either by mechanical inoculation or by aphids, Myzus persicae and Hyperomyzus sp. It infected plants belonging to three of the eight families tested, including lettuce, zinnia, aster, Chenopodium album, C. anthelminticum, and Gomphrena globosa. The last three plants developed only local lesions. Cucumber, tobacco, tomato, petunia, bean, broad bean, cowpea, turnip, corn, etc., were not infected.4) The virus was found to be carried over in the seed of lettuce. Seed-borne infection occured at a rate of 1 to 6per cent, in varieties Imperial 847, Great Lakes, and Wayahead.5) The virus activity was lost when juice of diseased lettuce was diluted 1:500, when exposed to 60°C for 10 minutes, or when subjected to aging in vitro for 2 days.6) From these results, it has been concluded that this virus is to be identified with the lettuce mosaic virus (Marmor lactucae), known from U. S. A. and other countries.