THE "TUBER-UNIT" METHOD OF SEED-POTATO 



IMPROVEMENT. 1 



By William Stuart, Horticulturist, Horticultural Investigations and Arlington Farm. 



INTRODUCTION. 



The ever-increasing importance of the potato crop makes it highly 

 desirable that more attention should be given to the subject of seed 

 improvement. As yet comparatively little thought has been given 

 to this phase of the potato industry by the American grower. The 

 European grower, on the other hand, recognizes the futility of at- 

 tempting to grow profitable crops of potatoes without giving the 

 most careful attention to the source of his seed supply. To this end 

 he either buys his seed from specialists in seed-potato production or 

 becomes a specialist himself. The result of this attention to the use 

 of good seed is well attested by the average yields secured. For the 

 years 1901 to 1910, inclusive, the average per-acre yield in bushels 

 was as follows: Germany 200.8, Great Britain 200.7, and the United 

 States 92.7. It would be absurd, of course, to claim that all of this 

 increase was attributable to good seed, but it is safe to assume that 

 good seed does play a very important role and should not be over- 

 looked by the American grower. 



DESCRIPTION OF THE "TUBER-UNIT" METHOD. 



The "tuber-unit" method was first recommended by Webber. 2 It 

 consists for the first year in the selection from the seed bin before 

 planting time of as many of the most perfectly shaped tubers as may 

 be desired by the grower. These tubers should be selected with 

 regard to type, size, and uniformity. Tubers ranging from 6 to 8 

 ounces in weight are preferred. Before planting, the selected tubers 

 should be treated by immersing them two hours in a formalin solu- 

 tion consisting of 1 pint of formalin to 30 gallons of water. In plant- 

 ing, each tuber is quartered and dropped as cut. This is done by 

 splitting the bud-eye cluster in four parts from seed to stem end 

 of the tuber. In other words, the tuber should be cut through its 

 longitudinal axis. The four pieces of each tuber are dropped con- 



1 Issued Feb. 15, 1913. 



2 Webber, If. J. Plant-breeding for farmers. New York Cornell Agricultural Experiment Station, 

 Bulletin 251, Feb., 1908, pp. 322-331. 



[Cir. 113] 25 



