A SPECIFIC MOSAIC DISEASE IN NICOTIANA VISCOSUM 
DISTINCT FROM THE MOSAIC DISEASE OF TOBACCO 
By H. A. Allard, 
Assistant Physiologist, Tobacco and Plant-Nutrition Investigations , 
Bureau of Plant Industry 
During the summer of 1915 many plants of Nicotiana viscosum and first- 
generation plants of the cross N . tabacum 9 X N. viscosum were grown 
in the field at Arlington, Va. Late in the season three plants of N. 
viscosum and one of the hybrid plants showed unmistakable symptoms 
of a typical mosaic disease. From the fact that the species viscosum 
and its hybrids had never before shown symptoms of disease from inocu¬ 
lations made with the virus of the ordinary mosaic disease of tobacco, 
these affected plants were taken into the greenhouse for further study. 
It has now been established that this mosaic disease affecting N. viscosum 
and its hybrids is biologically very different from the ordinary form of 
mosaic disease affecting varieties of N. tabacum , tomatoes (. Lycopersicon 
esculentum ), etc. Ordinary tobacco and also tomatoes appear to be quite 
immune from the type of mosaic disease in N. viscosum . Experiments 
have shown that this mosaic disease is infectious to plants of N. viscosum , 
although it appears that the disease is not as readily transferred by needle 
inoculations as the ordinary form of the mosaic disease, and longer periods 
of time are usually required before the disease comes into evidence. 
A number of distinct varieties of N. tabacum have been crossed with 
N. viscosum , including Maryland Mammoth, White Burley, and Connecti¬ 
cut Broadleaf. In these crosses the pollen of N. viscosum has been trans¬ 
ferred to the pistils of N. tabacum. In size, general appearance, and habit 
of growth first-generation plants of these crosses resemble much more 
closely the female parent ( N . tabacum) than the male parent ( N . vis¬ 
cosum) . In general appearance the leaves and blossoms also resemble very 
closely the leaves and blossoms of the female parent. These first-genera¬ 
tion plants inherit more strongly the visible physical characteristics of 
the female parent. They possess, however, certain physiological character¬ 
istics peculiar to the male parent (N. viscosum). This is indicated by the 
fact that they, like N. viscosum , appear to be immune to that form of 
mosaic disease which affects varieties of N. tabacum , but are susceptible 
to the mosaic disease affecting N. viscosum. The disease is readily ob¬ 
tained in these hybrids by grafting upon them scions taken from plants of 
N. viscosum. It is much more difficult to obtain the disease by needle 
inoculations. All phases of catacorolla in the blossoms and mottling and 
distortions in the leaves are shown in these hybrids affected with the 
Journal of Agricultural Research, 
Dept, of Agriculture, Washington, D. C. 
gl 
Vol. VII, No. n 
Dec. 11,1916 
G—101 
