DISEASE-KESISTANT VAKIETIES OF AMEKICA. 31 



Magnum Bonum aud Roj^al Kidne3^ The indorsement of these com- 

 parativel}^ late, white-fleshed, starch-rich potatoes in France and in 

 the other continental countries is the more signiticant when one 

 remembers that the chief aim with potato specialists there is to produce 

 the yellow-fleshed potato rich in protein. 



DISEASE-RESISTANT VARIETIES OF AMERICA. 



Until two or three years ago no systematic attempt was recorded, 

 so far as the writer has learned, to determine the relative resistance to 

 blight and rot of potato varieties in America. Of course this would 

 not imply that individual growers have not observed these difl'erences, 

 but they are rarel}' matters of record, and as a rule are based only 

 upon limited observations. Only two or three potato-seed dealers are 

 advertising disease-resisting varieties with an}^ prominence this year, 

 and these are in all cases comparatively new and little-tried sorts. 



INVESTIGATIONS AT THE EXPERIMENT STATIONS. 



Promising investigations have been inaugurated at several of the 

 State agricultural experiment stations which should soon supply data 

 for more reliable conclusions than are now possible. Woods," of the 

 Maine station, and Green, ^ of the Minnesota station, have each 

 reported results of variety trials as to disease resistance. 



Woods found a marked difi'erence in the ability of varieties to with- 

 stand both blight and rot. As a rule the earlier varieties were soonest 

 attacked. The variety Rustproof showed the highest degree of foliage 

 resistance and also the least rot, viz, only a little more than 1 per cent, 

 whereas the average of all varieties under trial was more than 30 per 

 cent. 



Green found that the loss from rot varied widely with varieties, 

 ranging from 1 per cent in the most resistant to 40 per cent in the 

 least resistant types. Potatoes of the type of Sir Walter Raleigh and 

 Rural New Yorker resisted rot better than those of an}' other class. 

 Of the 49 varieties tested, onl}^ two. Clay Rose and an unnamed seed- 

 ling, were practically free from rot. These trials will be continued. 



Observations on disease resistance have also been made by Macoun 

 at the Central Experimental Farm, at Ottawa, Canada. He has kindl}^ 

 advised the writer, in correspondence, of his conclusions. The follow- 

 ing varieties have shown especial disease resistance as judged by 

 appearance of blight on the foliage: Holburn Abundance and Pro- 

 fessor Maercker are most resistant, with Swiss Snowflake, State of 

 Maine, and Rural Blush onh^ a little less so. 



"Woods, C. I)., Maine Exp. Sta. Report, XIX: 181 (1903). 



''Green, S. B., Potatoes at the University Farm, Minn. Exp. Sta. Bui. 87 (1904). 



