20 DISEASE KESISTANCE OF POTATOES. 



RESISTANCE AS SHOWN TOWARD LATE-BLIGHT AND ROT. 



HISTORICAL STATEMENT. 



Doubtless examination of the earlier writings upon the potato disease 

 known as late-blight and rot would show that from the beginning of 

 its ravages differences have been observed in the resistance of varieties. 

 An}^ such records of the thirty years from 1845 to 1875 would have no 

 practical value now, since the varieties then in use have passed out of 

 culture; nor would they have much scientific significance, owing to the 

 lack of exact knowledge then as to the cause of disease. Going back to 

 the origin of the varieties still in cultivation, it is found that in the early 

 seventies an unusual anjount of attention was focused upon the matter 

 of the potato disease, as to causes and remedies. Ninety-four essays 

 secured by the Royal Agricultural Societ}^ of England in 1872 showed 

 agreement that an luiderl^^ng cause was the degenerac}' of the varieties 

 then in culture.'* The necessity for the production of new varieties 

 was emphasized. The introduction of improved American varieties 

 into England at about this period was most beneficial and stimulating 

 to the potato specialists of that country.-' These varieties were made 

 the parents in further breeding. The best production of this revival 

 was the JMagnum Bonum, originated by James Clark from a cross of 

 Early Rose with Victoria and introduced by Sutton in 1876. Experi- 

 ence with this variety laid the foundation for belief in possil)le disease 

 resistance in potatoes both in England and on the Continent. Magnum 

 Bonum soon became the standard main-crop variety of Great Britain 

 and so continued until within the last fifteen ^^ears, when it yielded to 

 Up-to-Date and others. It is still in considerable favor on the Conti- 

 nent. 



Charles Darwin in 1877-78 became interested in the possibilities of 

 disease-resistant breeding. Francis Darwin '^ states that Mr. James 

 Torbitt, of Belfast, bred and selected varieties to secure disease 



«See Jour. Roy. Agr. Soc. Eng., XX : 291 (1884). 



6 Dean, A. Potato Improvement in the Past Twenty-five Years. Jour. Eoy. 

 Hort. Soc, XII :41 (1890). 



Mr. C. G. Pringle, who was then the foremost potato breeder in America, states 

 that the demand from Europe for new American varieties was very active at that 

 period, and continued until tlie fear of the Colorado potato beetle led to the prohi- 

 bition by European governments of further importations of potato tubers from Amer- 

 ica. Thereupon I\Ir. Pringle supplied B. K. Bliss & Sons with specially hybridized 

 potato seed, which was sent abroad in considerable quantity. 



cLUe and Letters of Charles Darwin, II, pp. 519-522. 



The writer learns from Prof. T. Johnson, of Dublin, that Torbitt has been dead 

 some twenty years. He was in the wine trade and raised varieties of potatoes for 

 the berries, or seed balls, which he used as a source of material for wine. All of 

 his varieties have disappeared except onfe coarse, red one, which was. and is proof 

 against disease. 



