Studies on the asparagus-bean mosaic virus

Abstract

The causal virus of mosaic disease of asparagus-bean and cowpea in Japan was investigated and the following results were obtained:1) This virus was easily transmissible by pressed juice and also by aphids, Myzus persicae and Aphis medicaginis. Transmission tests with A. gossypii were unsuccessful. Both acquisition and inoculation feeding thresholds of Myzus persicae were between 10 and 15 seconds.2) Seed transmission rate of this virus was 0.24 per cent in the case of Vigna sesquipedalis, when 2914 seedlings were used for the test.3) Among 38 species of Leguminosae and 8 species of non-leguminous plants tested, the susceptible plants were shown to be as follows: Astragalus sinicus, Canavalia ensiformis, Phaseolus angularis, P. lunatus, Vigna sesquipedalis, and V. sinensis. All these species produced systemic mottling. Cassia tora formed only black local lesions. Phaseolus vulgaris formed faint chlorotic local lesions, or caused symptomless local infection, but some varieties were immune from the disease. Aeschynomene indica and Canavalia gladiata were symptomless carriers. Vicia faba formed reddish-brown local lesions, but was not systemically infected.4) Thermal inactivation point of this virus lay between 55 and 60°C. Longevity in vitro was found to be between 12 and 24 hours. Dilution-end point was between 1: 1, 000 and 1: 2, 500.5) Strains isolated from seed-borne diseased asparagus-bean plants found to be almost the same in respect to host range, physical properties, and transmission.