PERMANENCE OF VARIETY IN THE POTATO 1 
By Fred A. Krantz 2 
Division of Horticulture , Minnesota Agricultural Experiment Station 
The practice of selection within the clone in order to maintain and 
improve the productivity and quality of potato varieties is of compara¬ 
tively recent origin. In the early period of potato improvement, hy¬ 
bridization with subsequent selection of the most promising seedlings 
was the method employed. The practice of vegetative selection is 
founded for the most part on the success of numerous attempts to iso¬ 
late high-yielding and low-yielding strains. Many investigators con¬ 
sider that the greatest benefit to be derived from selection is the main¬ 
tenance of the optimum vigor of the variety, while other investigators 
believe that the results indicate the presence of inherited differences 
within the variety and have therefore considered selection to be of 
value in the improvement of varieties. Recent advances in the knowl¬ 
edge of certain diseases hitherto unrecognized have thrown considerable 
doubt upon the correctness of the latter interpretation. This study 
has for its primary object a determination of the effect upon the variety 
of selection as practiced by growers and a determination of the stability 
of regional differences, when the disease factor is eliminated. 
REVIEW OF LITERATURE 
The older theory suggested by Knight (jo ) 3 and Aitken (i) of varietal 
senility has given place to that of the deterioration of seed stock. Since 
selection has for one of its primary objects the prevention of this deterior¬ 
ation, a brief historical review of these theories will be of interest. 
As early as 1787 William Marshall ( 12 ), writing from England, reported 
that potato varieties were transitory in each district. He noted that the 
declining varieties were characterized by curled tops. Cathcart ( 3 ) 
quotes Stephens' ( 19 ) “ Book of the Farm" as authority for the statement 
that the condition of curl was first observed in 1764. Marshall ( 12 ) 
considered curl to be due to varietal senility, as it was noted that new 
varieties secured from seed were not subject to this condition. The 
following statement by Knight (9), in 1807, indicates the transitory 
nature of potato varieties at that time. 
Dr. Hunter [ 5 ] in his Georgical Essay, I think, has limited the duration of a variety 
in a state of perfection to about fourteen years; and probably taking varieties in the 
aggregate, and as the plant is generally cultivated, he is nearly accurate. 
1 Accepted for publication Feb. 15, 1922. Paper 298 of the Journal Series of the Minnesota Agricultural 
Experiment Station, published with the approval of the Director. 
* The experiment was originated by A. W. Aamodt, who collected the original lots of potatoes, took 
descriptive data, and supervised the planting in the spring of 2917. The work was carried on under the 
supervision of Richard Wellington from the time of its inception until the spring of 1919. Thanks are due 
to O. I. Bergh, of the Nmth Central Substation, Grand Rapids, Minn., Mark Thompson, of the Northeast 
Substation, Duluth, Minn., and Thomas McCall, of the Northwest Substation, Ciookston, Minn., for 
their cooperation. 
* Reference is made by number (italic) to “literature cited,” p. 959-961. 
Journal of Agricultural Research, 
Washington, D. C. 
Vol. XXIII, No. 12 
