POTATO BREEDING AND SELECTION. 25 



fall of 1903 a field of potatoes was selected the variety of which was 

 known to be pure, and in a place where the soil was uniform 100 

 consecutive hills were dug and weighed separately. From these 100 

 hills the 25 heaviest and 25 lightest yieldmg hills were selected. 

 This process was repeated until 125 hills of each had been secured. 

 In the following spring 10 rows of 232 plants each were planted from 

 the heaviest yielding hills and 5 from the light-yielding ones. The 

 resultant yields averaged 362^ bushels per acre from the productive 

 hills and 339^ bushels from the unproductive, the gain in favor of 

 seed from the heaviest yielding hills being at the rate of 23^ bushels 

 of marketable tubers per acre. 



It was found that the amount of variation in the yields of adjacent 

 hills in the 1904 crop was almost as great as in that of the original 

 stock. The 1904 variations were 11.9 ounces, or 39.18 per cent, as 

 against 9.37 ounces, or 39.44 per cent, in the 1903 crop. In this 

 connection Eustace says: 



That the variation was not materially reduced by the uniform conditions under 

 which the experiment was made was a surprise. The conclusion is that factors which 

 are apparently unimportant produce wide differences in yield. 



From our present knowledge of the behavior of individual hills of 

 potatoes, it seems quite certain that Eustace would have secured 

 much more uniform results had the progeny of each individual hill 

 been planted separately. In mass plantings individual variations 

 are obscured, rather than emphasized, as in the tuber-unit or progeny- 

 row method. 



At the annual meeting of the American Breeders' Association, in 

 1907, Waid ^ reported the results of studies which he had undertaken 

 at the Ohio xigricultural Experiment Station, in which the progeny 

 from productive and unproductive plants in 1903 had been carefully 

 studied during 1904, 1905, and 1906. The results of this work showed 

 quite clearly that with few exceptions low-yielding plants remained 

 unproductive. 



The 3-year average from high and low yielding plants was found to 

 be 1 .38 pounds for the former and 0.73 pound for the latter, or a differ- 

 ence of over 89 per cent. A comparison of yields from the productive 

 plants and plants from common stock showed a gain of over 25 per 

 cent for tin; former. 



A further study of Waid's data reveals the fact that the average 

 weight of the 10 original higli-yielding hill selections was 2.38 pounds 

 per phmt, whereus (he 3-year average of their progeny was only 1.38 

 pounds per plant. This suggests that in the selection of high-yielding 

 hills onc! is not at all certain what proportion of (he hills is likely to 

 maintain their seemingly productive; character. 



• Wald, C. W. RemiltA of hill wlectlon of seed potatooR. In Amer. Breeders' Assoc, 3d Ann. upi., 

 1W7, p. 191-198. 



