32 DISEASE RESISTANCE OF POTATOES. 



WORK AT THE VERMONT STATION. 



The most extensive work on potatoes has been done b}^ Stuart, who 

 two 3^ears ago inaugurated at the Vermont station variety trials as- to 

 disease resistance, supplemented by breeding experiments. Professor 

 Stuart has kindly supplied the following summar}^ of his results to 

 date:** 



Eight varieties were under trial in 1903 — Dakota Red, Enormous, 

 Green Mountain, Rustproof, Squire, Sir Walter Raleigh, and two of 

 Manum's unnamed seedlings. In 1904 the same varieties were used, with 

 the addition of June, Mammoth Gem, Minister, New Queen, State of 

 Maine, Sutton's Discovery, nine more of Manum's seedlings, S. coin- 

 mersonll from Doctor Heckel, of Fi-ance, a Peruvian variety from the 

 United States Department of Agriculture at Washington, and four 

 Mexican varieties furnished by Mr. C. G. Pringle. The latter included 

 two cultivated varieties termed Monterey and Mexican, and the two 

 wild species, S. polyadenuuii and S. stoloniferum. Observations have 

 been made as to both foliage and tuber resistance. As to foliage, none 

 was wholly free from blight, but there was a marked difference, some 

 being quickly and entirely destro3'ed, while others suffered only 

 slightl}^ In 1903 Rustproof headed the list in this respect, and Dakota 

 Red was second. In 1904 those showing greatest foliage resistance 

 were as follows, in the order of their resistance: Monterey, S. com- 

 mersonii^ S. polyadenium., Rustproof, Sutton's Discovery, June, Mex- 

 ican, Mammoth Gem, and Manum's No. 3. Dakota Red did not equal 

 its 1903 record. 



Judged b}' resistance of tubers to rot, Dakota Red made the best 

 showing of the varieties which were tested for two seasons, but there 

 was some rot in it both 3'ears. Of those added to the series of 1904 

 several varieties gave a crop of tubers entirely free from rot, namely 

 8. polyadenium^ S. coinmersonii^ Sutton's Discovery, June, and the 

 two Mexican varieties. It is noteworthy that these are likewise the 

 varieties which showed the least blighting of the foliage. Possibly 

 the absence of rot is in some degree attributable to the lessened amount 

 of infection of tubers from vines in consequence of this, although there 

 were adjacent plants showing badly diseased foliage. 



Selection. — In 1903 a few plants in the varieties grown v/ere observed 

 to remain green longer than the others. The tubers from these were 

 saved and were planted in 1904 along with others of the same variet}^ 

 that succumbed much earlier. So far as could be noted no increased 

 disease-resistant qualities were transmitted to the offspring of these 

 plants. 



«For further details see Stuart, W., Disease-Resistant Potatoes, Vermont Exp. Sta. 

 Bui. 115 (May, 1905). 



