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Disease Resistance in Varieties of Potatoes. 



By C. R. Obton. 



This report is ttie result of experiments conducted by tlie author, 

 under the direction of Dr. L. R. Jones, wliile in the cooperative employ 

 of the Vermont Experiment Station and the United States Department of 

 Agriculture, Bureau of Plant Industry, during the fall of 1909-10." In 

 general, the work was the outgrowth of a series of experiments carried 

 on by Professor William Stuart at the Verjuont Station for several years 

 previous to 1909, the results of which may be found in Bulletin 122, Ver- 

 mont Experiment Station. In particular, it was the development of some 

 research work of the previous winter on late blight. Professor Stuart 

 conducted his experiments in the field upon over 1.50 varieties, with the 

 idea of determining, if possible, the disease resistant qualities of botli 

 American and European varieties of ];otatoes, to the late blight, Phytoph- 

 tliora infestans (Mont) Bary, a fungus which causes the loss of many 

 thousands of bushels of potatoes yearly in New England, especially in 

 Maine and Vermont, and periodically the loss of one-half the entire crop 

 or more in that section. 



European potato growers have for years been breeding and testing 

 potato varieties for the disease resistant quality, until they have developed 

 a series of varieties which liave jiroved by held trials to be highly resistant 

 to fungous diseases. The processes as carried out by them necessitated 

 growing the tubers for several years in succession and noting the amount 

 of infection each year. This, of course, is at best a tedious operation, giv- 

 ing slow and often unsatisfactory results. 



In 190S Mr. N. J. Giddings, then of the Vermont Experiment Station, 

 found that resistance to the late blight could be determined with some 

 degree of accuracy by artificial inoculation of the tubers, with pure cul- 

 tures of the fungus, under sterile conditions in the laboratory. The value 

 of the laboratory method for testing varieties of potatoes for disease re- 

 sistance is easily seen when we consider that it would permit us in two 

 or three weeks to test the resistance quality of any variety, a process which 



* The full vesiilts of these experiments are to be published in a foi'thcoming 

 bulletin of tho T'nited States Department of Agriculture, Bureau of Plant Industry. 



