Abstract
In the course of research studies to detect the antiviral substances for tobacco mosaic virus (TMV) and cucumber mosaic virus (CMV), it was found that some salts of alginic acid have a high inhibitory activity against TMV infection.The methods used are the inoculation of mixture of chemical and virus, and the inoculation of virus after application of chemicals on the leaf surface. Na-, K-, NH3- and triethanolamin-salt of alginic acid showed the same degree of inhibitory activity, 80-100 percent inhibition, in the tests using 0.1-1 percent concentration of chemicals and TMV-Nicotiana glutinosa as the test combination. Equally high inhibitory activity was observed also in the combination of TMV-French bean and TMV-Xanthi nc tobacco, by the test using Na alginate. In TMV-Chenopodium amaranticolor, however, the activity was lower than those in the other combinations mentioned above.
The mixture of Na alginate and casein (AC) showed higher inhibitory activity and retained the activity longer than Na alginate alone after application to N. glutinosa leaves. AC inhibited about 30 percent of the transmission of CMV to tobacco plant by green peach aphid in the green house experiment.
Mechanism of the inhibitory activity of alginic acid is not clear yet. However, following data were obtained; 1) When Na alginate was applied to the undersurface of leaf and TMV was inoculated on the opposite surface, no effect was observed. Accordingly, there was no sign of translocation of effective substances into the leaf tissues. 2) When mixed solution of TMV and Na alginate was centrifuged at low speed, most infectivity was found in the precipitation. This fact shows that AC has the effect to aggregate TMV particles. 3) No inhibitory activity was found when AC was applied after inoculation, except with in 5 minutes after inoculation. 4) Infection of Bright Yellow tobacco which can be infected systemically with TMV was also inhibited by AC. This fact indicates the effect of AC is not the prevention of local lesion formation but the inhibition of infection itself. The results of further tests including practical application in the fields shall be reported eleswhere.
