Hayes and Garber - Cucurbit Breeding

POTATO IMPROVEMENT 231
toes has been traced to certain plant diseases (Stewart, 1916;
Orton, 1914) which have been variously named as leaf roll,
mosaic, and curly dwarf.
Quanjer (1920) has presented evidence
to show that these three diseases may be stages of the same
disease, which is transmissible from plant to plant. Similar
results have been obtained at University Farm. 1 The disease
is called " mosaic dwarf" by Krantz and Bisby in unpublished
investigations. That rejuvenation of a variety is possible
through its introduction and growth under a more favorable
environment is illustrated by studies which have been carried on
FIG. 57. Progeny of single tubers as grown at University Farm, 1918.
Some tubers give vigorous progeny, others produce only small, weak, degenerate
plants. (Courtesy of Krantz.)
cooperatively between the Division of Horticulture of the Minnesota
Central Station and the sub-stations. Yields for Minnesota
No. 2 at University Farm for 1914, 1915 and 1916,
respectively, were 196, 169 and 22 bu. This shows the rapid
reduction in yield which is obtained by the continued use of
tubers saved at University Farm. Tubers of Minnesota No.
2 saved from the 1916 University Farm plot gave a yield cf
170 bu. at Duluth in 1917. Tubers from this Duluth plot yielded
300 bu. at Grand Rapids in 1918. Whether a badly diseased
1 Data on running out and on field experiments in Minnesota were
furnished by F. A. KRANTZ of the Division of Horticulture, Minnesota
Experiment Station.