Inativação do vírus do mosaico comum do fumo pelo filtrado de culturas de Trichoderma sp

Abstract

Trichoderma sp. grown in liquid medium produced a substance which has caused up to 90% reduction in the infection capacity of the tobacco mosaic virus, measured in number of local lesions on Nicotiana glutinosa half leaf inoculations. Under the present experiments the fungus has been grown in liquid medium and the filtrates used in inactivation tests on the virus. From the fact that the liquid filtrate showed inactivation power after only two days of culture it is concluded that the inactivation is of the nature of a secretion of the fungus into the liquid medium. The inactivation proceeded within 2 minutes after mixture of the culture extract with the virus, no better results were obtained if the mixtures allowed to stand for a longer period of time. If cultures were grown in the light in the laboratory the inactivation power decreased after the second day as was found by Weindling (8), for the effect on Rhizoctonia sp. If grown in the dark the inactivator continues to increase in concentrations for at least 22 days. In the dark no spores formation could be observed. Physiological activity associated with spores formation may be the reason for the loss of inactivator in day light grown cultures where spores start to be formed after the second day of growth. Extraction of the inactivator with chloroform was attempted according to Weindling's method. The inactivator could never be completely extracted since the treated filtrate kept showing inactivation on tobacco mosaic virus. This suggests that the inactivator for the virus may be a different from the one found by Weindling against Rhizoctonia sp. By ultracentrifugation at 35,000 r.p.m. no inactivator could be obtained from the filtrate. Using Takahashi's acetone method a whitish precipitate could be obtained which showed an inactivation of tobacco mosaic virus.