|Budget Amount *help
¥6,600,000 (Direct Cost: ¥6,600,000)
Fiscal Year 1987: ¥800,000 (Direct Cost: ¥800,000)
Fiscal Year 1986: ¥500,000 (Direct Cost: ¥500,000)
Fiscal Year 1985: ¥5,300,000 (Direct Cost: ¥5,300,000)
Several crops cultivated in Japan were surveyed for the occurrence of mixed virus infections. The major combinations of viruses found in cucurubit plants included cucumber mosaic virus (CMV), watermelon mosaic virus-2 (WMV-2), and zucchini yellow mosaic virus (ZYMV), in potatoes, potato virus Y, potato virus X and potato leaf roll virus, in tomato and pepper, tobacco mosaic virus and CMV, in spinach and Chinese mustard, turnip mosaic virus and CMV. Frequency of mixed virus infection was high in cucurubit plants, potato and Chinese mustard, in decreasing order. Under the experimental conditions, symptoms on host plants caused by double infection of potyviruses and non-potyviruses could be classified into 4 groups. a) Symptoms characteristic of non-potyviruses only, b) Symptoms characteristic of both viruses, c) Symptoms characteristic of potyvirus only, d) New types of symptoms not characteristic of either viruses. In cucumber plants doubly infected with WMV-2 and CMV or ZYMV and CMV, or ZYMV and cucumber green mottle mosaic virus, the concentration of WMV-2 and ZYMV decreased significantly compared with that in single infection. In contrast, the concentration of CMV increased significantly more than that in CMV singly infected plants. In trunip plants doubly infected with TuMV and CMV, or tobacco plants doubly infected with PVY and CMV, the concentration of eithqer virus was not significantyl altered from the usual level in single infection. Transmission rate of CMV by aphids from doubly infected cucumber plants increased by about 27 % of that in single infection.