Abstract
1) In Japan, melon mosaic virus (Lindberg et al., 1956) has been found infecting squash, pumpkin, white gourd, and oriental pickling melon (Komuro, 1957). The same virus has recently been detected also from cucumber plants showing veinal necrosis and/or mosaic. The diseased plants have been collected from Kochi, Iwate, Saitama, and Tokyo. In the samples from Iwate and Kochi, and some of the samples from Saitama, the symptoms were characteristic necrotic leions along veins, in which the affected parts were dry and brittle. There were some malformation of the leaves and some shortening of the internodes, but mosaic was not observed. The samples from Kochi showed small interveinal necrotic spots accompanied with the veinal necrosis. The samples from Tokyo and some samples from Saitama showed mosaic, but the pattern was coarser than in the mosaic caused by cucumber mosaic virus. Most of them showed no necrosis. A few samples from Saitama showed both veinal necrosis and coarse mosaic.
2) The symptoms on cucumber plants (varieties Shinsairaku and Shin-T-go) mechanically inoculated with the melon mosaic virus were veinclearing and coarse mosaic. Some individuals showed veinal necrosis which was the same as that observed in the samples from Iwate and Saitama. Necrotic spots as observed in the samples from Kochi, however, could not be reproduced.
3) A mosaic disease of watermelon was found severely occurring in a field in Okinawa, the Ryukyu Islands, and from the diseased plants, the same virus was isolated.
4) By mechanical inoculation tests, the melon mosaic virus was found to infect, in addition to the hitherto reported hosts, pea, broad bean, and okra, symptoms on these plants being veinclearing and mosaic. In hot summer months, however, it is rather difficult to infect pea and broad bean.
