10 BULLETIN 1156, U. S. DEPARTMENT OF AGRICULTURE. 
Table 1. — Reaction of American and European potato varieties to potato wart — Contd. 
Group and variety. 
Source of seed. 
Years 
tested. 
Tests 
made. 
Wart re- 
action. 
1 
1 
2 
) 
3 
4 
5 
English and Scojch varie- 
ti e s— Cont inue d . 
Field Laboratory, Prince Edward 
Island. 
Board of Agriculture and Fisheries, 
London, England. 
2 
3 
2 
3 
3 
1 
1 
2 
2 
1 
2 
2 
2 
2 
2 
1 
1 
2 
1 
3 
1 
1 
2 
2 
3 
3 
2 
3 
2 
3 
3 
1 
1 
2 
2 
1 
2 
2 
2 
2 
2 
1 
1 
2 
1 
3 
1 
1 
2 
5 
3 
3 
o 
Irish Queen 
o 
Kerr's New Pink ' 7 
o 
Kerr's Pink 
Board of Agriculture and Fisheries, j 
London, England. 
o 
o 
Langworthy 
do 
o 
Field Laboratory, Prince Edward 
Island. 
Board of Agriculture and Fisheries, ' 
London, England. 
do 
o 
o 
o 
Mauve Queen 
do 
o 
Ma v Queen 
do 
o 
Midlothian Early 
do 
4- 
Nithsdale ." 
do 
o 
Provost 
do ' 
o 
Rector 
do 
o 
.do. 
o 
Rhoderick Dhu 
do 
o 
St. Malo Kidne}' 
do 
o 
Scottish Triumph 
Field Laboratory, Prince Edward 
Island. 
Board of Agriculture and Fisheries, 
London, England. 
?0 
Shamrock 

Sharpe's Express 
H- 
Board of Agriculture and Fisheries, 
London, England. 
do 
do 
do 
do 
o 
Templar 
Tinwald Perfection 
White Citv 
Witch Hill 




» One waited hill was found of this variety in 1920; it was saved separately from the uninfected hills, 
and both were planted in 1921. The progeny of the warted hill showed 40 per cent infection; the progeny 
of the wart free hills were not infected: the former are therefore believed to have been rogues. In plats of 
this variety grown by the State Department of Agriculture of Pennsylvania no infection has ever been 
observed. 
In addition to the varieties included in Table 1, tests have been 
made of an extensive collection of seedlings bred by William Stuart, 
of the Bureau of Plant Industry. Two principal ends have been 
sought in these seedling trials: (1) The immediate attainment of 
new types of immune potatoes which might show superior adaptation 
to the climate and soil of the wart-infested areas and hence might 
be introduced into general culture and (2) the development of infor- 
mation upon the inheritance of susceptibility and immunity in the 
progeny of crosses which combine in various ways immune and sus- 
ceptible parents. Two preliminary reports upon the results of these 
studies have appeared. 10 
To date, 194 seedlings, practically all of known parentage, have 
been grown on the wart plats at Freeland, Pa. Of these seedlings 
12 appear to be certainly immune and 48 have resisted or escaped 
infection in a single test. Of the 12 immunes, 7 have been under 
observation for four years and 5 have been tested for three years. 
In stability of the immune character and in commercial value, these 
seedlings are comparable with the named varieties; and further tests 
may demonstrate that superior-yielding immune types are already at 
10 Lyman, G. R., and others. Op. cit. 
Orton, C R., and Weiss, Freeman. The reaction of first-generation hvbrid potatoes to the wart disease. 
In Phytopathology, vol. 11, pp. 306-310. 1921. 
