| OCR Text |
Show 1938] Blood, Watson: Tobacco Mosaic Virus No. I in Datura 19 mosaic virus inoculated, it appeared first in the streaked secondary shoot and then spread to involve the entire plant. Therefore, the sequence of the symp following consecutive inoculations with the two viruses appears to be unlike the sequence observed when the systemic virus deevlops on D. meteloules plants as the result of an inoculation with tobacco mosaic virus no. 1. The effect of inoculating the tobacco mosaic virus no. 1 on Datura meteloides plants infected with the systemic virus. Twenty D. meteloules plants were inoculated with the systemic virus, and as soon as the systemic symptoms developed the plants were inoculated with the tobacco mosaic virus. No new symptoms developed. The same plants were inoculated again with the tobacco mosaic virus; and again the systemically infected plants showed none of the usual necrotic signs of the tobacco virus. The experiment was repeated with the same results. It was concluded that the systemic virus was able to protect or immunize the D. meteloides plant from the necrotic symp toms toms of the tobacco mosaic virus. Effect of inoculating Datura meteloides and tomato with tobacco mosaic virus no. 1 and the systemic virus The tobacco simultaneously. mosaic virus no. 1 and the systemic virus were mixed in equal proportions and inoculated on 25 D. meteloides, and on 20 tomato plants. The D. mete loides plants inoculated with this virus mixture necrotic symptoms developed on the leaves in 3 days and later the pronounced streaks of the stem. The upper uninoculated leaves of the plant developed the systemic symptoms with no necrosis on about the seventh day. Since the systemic virus as it develops on D. meteloides from the tobacco mosaic virus does not appear for some time after the inoculation with tobacco mosaic, and since the sequence of de velopment is quite different, the conclusion that the systemic development is due to a change occurring in the tobacco virus itself and not to the presence of a virus mixture of some sort appears to be justified. The tomato plants inoculated with the combination of tobacco mosaic and systemic viruses developed and typical tobacco mosaic symptoms after about 7 days. A transfer was made from the tomato to D. meteloides plants. In about 3 days the D. meteloides plants produced the necrotic spots and stem streak, but there was no subsequent systemic symptom development following the usual incubation period. It was concluded that the tobacco mosaic virus no. 1 is dominant over or is able to take precedence over the systemic virus when the two are inoculated together on the tomato, which mayor may not be significant. The nature of the development of systemic symptoms, the protection of the systemically infected host from tobacco mosaic virus no. 1, the predomi nance of tobacco mosaic virus no. 1, together with the similarity of the systemic virus and tobacco mosaic in physical properties and the existence of differential hosts indicate that the systemic virus may be a permanent modi fication of the tobacco mosaic virus no. 1 occurring within the tissues of the host plant D. meteloides. |
