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Disease RESISTANCE IN VARIETIES OF POTATOES. 
By C. R. ORTON. 
This report is the result of experiments conducted by the author, 
under the direction of Dr. L. R. Jones, while in the codperative 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 Vermont Station for several years 
previous to 1909, the results of which may be found in Bulletin 122, Ver- 
mont Experiment Station. In particuiar, it was the development of some 
research work of the previous winter on late blight. Professor Stuart 
eonducted his experiments in the field upon over 150 varieties, with the 
idea of determining, if possible. the disease resistant qualities of both 
American and Buropean varieties of potatoes, to the late blight, Phytoph- 
thora infestans (Mont) Bary, a fungus which causes the loss of many 
thousands of bushels of potatoes yearly in New Wagland, 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 have proved by field 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 1908 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 vatue 
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 
1The full results of these experiments are to be published in a forthcoming 
bulletin of the United States Department of Agriculture, Bureau of Plant Industry. 
