Sept. 1.1920 Line-Selection Work with Potatoes 571 



At present, selection based chiefly on vine characteristics seems to be 

 the only hope in dealing with degeneration. The success of such selec- 

 tion is measured by one's ability to identify intermediate types as well 

 as typical curlydwarf degenerates. 



A special seed plot in which the seed pieces from each tuber are planted 

 in consecutive hills promises to afford the best solution of the problems 

 of degeneration and the maintenance of high-yielding variety populations. 



Seed for such a plot may be selected in one of two ways. Especially 

 vigorous hills may be marked in the field during the growing season, and 

 the crop from these may be dug and used for planting the special seed plot 

 of the following season, or seed may be selected in the field at digging time 

 or from the bin. The first method will insure the greater return from the 

 first seed plot, especially if the field from which the seed is selected con- 

 tains a large percentage of degenerate plants. In selecting seed in the 

 field after the digger or from the bin, one may to a certain extent avoid 

 degenerate types by observing certain tuber characteristics, (i) Choose 

 seed tubers rather above the average size for the variety. (2) Select 

 those that are long rather than short lor the variety and with both ends 

 full and rounded, not pointed. (3) Choose those that are oval rather 

 than round in cross section, or, in other words, flattened tubers. (4) Pick 

 tubers with conspicuous and moderately deep eyes. 



The seed plot can best be planted by hand. The rows should be spaced 

 the usual distance apart and the hills placed 12 or 15 inches apart in the 

 row. On good, fertile, irrigated land, where the recommendations in 

 regard to thinning are to be carried out, the hills should be spaced at 

 12 or even 10 inches apart. The tubers should be taken to the field 

 whole and then cut as planted. The seed pieces may be cut rather small 

 if seed is not abimdant. Single-eye seed pieces weighing from X to i 

 ounce will give just as good results as larger pieces. These are conven- 

 iently planted with a hoe, and if small should not be covered over 3 inches 

 deep. Each tuber is cut by itself, and the pieces are dropped in con- 

 secutive hills. Not only is it important to have the hills from each tuber 

 in a group, but it is desirable to have these groups marked off one from 

 the other. This may be accomplished in several ways. A good way is 

 to drop a hill of corn between the groups. The important point, however, 

 is to have the hills from each tuber in a group. This is the only way if 

 intermediate types are to be eliminated from the seed plot by roguing. 

 Mixtures are also easily detected where the hills are in tuber groups. 



The seed plot should be thinned by removing all but one stalk from 

 each hill. Thinning should be done as soon as the vines are large enough 

 to pull, usually from five to six weeks after planting. Proper compari- 

 sons can best be made between hills with a uniform number of stems, and 

 this is the real object of thinning. But single-stemmed hills also produce 

 tubers of a more uniform size, and this is desirable, especially if the seed 

 stock is to be offered for sale. Regardless of the merits of the case, the 

 public commonly thinks of good potato seed as uniform-sized stock. 



