Abstract
Both WYMV and BYMV in the leaves of diseased plants, which were dehydrated at temperatures ranging 0∼2°C and were stored in the absence of oxygen at 5∼10°C, showed considerable infectivities even after about two years.
By continuously conducted experiments concerning the infectivity of soil particles of clay fraction separated from WYMV- or BYMV-infested soil, it was confirmed that the infectivity of the clay fraction with particles less than 2μ in diameter was much greater than that of the fraction with particles larger than 2μ, and that there are found in the pellet of clay particles neither any special soil-inhabiting microorganism to be regarded as a possible vector nor any large fragment of plant tissue such as root hair.
Moreover the possibility was shown that both WYMV and BYMV preserved their activities at least during the period from season to season if these viruses are adsorbed (under certain favorable conditions) in some mineral clay particles or in some sterilized soil particles.
These findings seem to justify the writer's view that these ordinary soil-borne viruses exist adsorbed in soil particles of clay fraction which include organic colloidal substances such as fragments of humus as well as mineral clay particles with the ability to adsorb proteins, and that neither the presence of soil-inhabiting microorganism nor of even a fragment of root of diseaed plant is necessarily needed to explain the considerable longevity of these soil-borne cereal mosaic viruses in the soil.
