Potato Breeding 69 



ceding year, go over the product of each select tuber-unit and pick 

 out the ten best tubers of each for the next year's planting. 



Continuing selections in third year. — In the third year, the fifty 

 selections of heavy yielding tuber-units should be planted by the 

 same method used the second year, at least forty hills of each selec- 

 tion being planted. The row from each unit should be plainly la- 

 beled or otherwise marked to avoid mixing the pedigree. Treat this 

 breeding-plot as described for the breeding-plot in the second year, 

 weigh up the product of each four-hill tuber-unit in the same way to 

 determine which unit of the second year's selection has transmitted 

 in greatest degree the tendency to yield heavily. Finally, select 

 again the best fifty tuber-units to continue the breeding, and retain 

 the good tubers of discarded units to plant a multiplication in the 

 fourth year. 



In the third year, a multiplication-plot should be planted with the 

 good tubers from the discarded tuber-units of the breeding plot of 

 the second year. In planting this plot the grower can use any 

 method of cutting and planting the tubers which he thinks most 

 desirable. This plot should give enough seed to plant a fairly large 

 plot in the fourth year. 



Continuing selections in fourth and succeeding years. — In the 

 fourth and succeeding years the selection should be conducted by 

 the same plan as outlined above. When this system is well under 

 way, it will be seen that each year the breeder is growing a small 

 breeding-plot, a large multiplication-plot for seed and a general 

 crop. 



Further considerations. — As the selection progresses many of the 

 strains from the original fifty tuber-units will be entirely discarded. 

 The breeder must be continually watching for the appearance of a 

 heavy yielding strain, and if such a strain is discovered, all of the 

 fiu-ther selections should be made from this strain. 



In advocating the selection of but fifty tuber-units and the 

 planting of ten tubers only from each select unit the writer has 

 had in mind the reduction of the work to a comparatively siniple 

 plan which would be better to handle larger numbers if the grower 

 is so situated that he can take the time for it. It is, however, better 

 to use comparatively small numbers carefully than to attempt to 

 handle large numbers and find the work too extensive. 



