Journal of Agricultural Research 
Vol. XXV, No. a 
90 
POTATO AND NIGHTSHADE 
Seed from a volunteer plant of common nightshade was planted in 
steam-sterilized soil in the greenhouse at Orono in the winter of 1919-20. 
The seedlings were transferred to similar soil in small pots and grouped 
in five series, as follows. 
Series 1 
Spinach aphids were transferred from mild mosaic Green Mountain 
potato plants to 13 caged nightshade plants growing in nine pots and 
were killed a week later by fumigation. The results, together with other 
data, are given in Table XXIII. Table XXIII shows that 2 of the 13 
nightshade plants were certainly mosaic in appearance and 7 others could 
be placed almost in the same class (PI. 15, D). The only plants that 
showed no mosaic symptoms were 3 that were smaller, when the 
aphids were introduced, than others in the same pots. Probably they 
were not fed upon by the aphids. The first mosaic symptom, leaf curling, 
appeared in from 20 to 47 days after inoculation. 
Table XXIII. — Transference of aphids from mosaic potato plants to healthy nightshade 
plants 
Aphids introduced. 
Date of appearance of mosaic symptoms. 
Pot 
No. 
Number 
of leaves 
Number. 1 
Date. 
on plant. 8 
Leaf curl. 
Leaf 
collapse. 
Wrinkling. 
Complete. 
1 
70 
Feb. 17 
{ * 7 
Mar. 16 
None. 
Mar. 25 
None. 
Mar. 31 
None. 
Apr. 6. 
2 
40 
...do. 
6 
Mar. 16 
...do. 
...do. 
3 
50 
.. .do. 
7 
...do. 
Mar. 25 
Mar. 31 
Not Apr. 26. 3 
4 
60 
Feb. 24 
9 
...do. 
...do. 
Apr. 6 
Do. 
5 
95 
...do. 
8 
Mar. 31 
Mar. 31 
Mar. 31 
Apr. 12. 
f 7 
Apr. 6 
None. 
Apr. 6 
Not Apr. 26. 3 
6 
80 
...do. 
i 4 
None. 
...do. 
None. ' 
1 t 
...do. 
...do. 
...do. 
7 
50 
...do. 
8 
Mar. 25 
Mar. 25 
Mar. 31 
Do. 3 
8 
80 
.. .do. 
7 
Mar. 16 
Mar. 31 
Apr. 6 
Do. 3 
A 
80 
...do. 
/ 7 
Mar. 25 
Mar. 25 
...do. 
Do. 3 
y 
l 5 
Apr. 12 
None. 
Apr. 12 
! 
Do. 3 
1 Approximate. 
8 Over 1 cm. in length, including the cotyledons. 
* Probably mosaic, however, even though not completely so. 
Series 2 
Healthy controls to Series 1, with each of five plants in a separate pot, 
were fed upon for a week by 40 to 100 aphids. The aphids were intro¬ 
duced on March 8 when there were eight or nine leaves each over 1 cm. 
in length. No mosaic symptoms had appeared on April 26, when all 
plants were discarded, in marked contrast to those of Series 1 growing 
alongside (PI. 15, D). 
Series 3 
On February 9, 1920, juice expressed from mild mosaic potato plants 
was inoculated into the mutilated leaves of 10 nightshade plants when 
the number of leaves over i cm. long was from three to eight. Only 
