Reed : The mildews of the cereals 383 



c 



dispersa, the form Secalis on rye, and the form Tritici on wheat. 

 Eriksson sowed uredospores from the infected hybrid upon three 

 rye plants and also upon three wheat plants of the same age. 

 Eleven days later a rich growth of the rust appeared upon the in- 

 oculated areas oi the wheat plants. No infection occurred on the 

 rye, although the plants were kept several days longer. It \s 

 apparent, then, that this hybrid had a well-marked resistance to 

 the form Secalis of Puccinia dispersa, and was entirely susceptible 

 to the form Tritici, 



Some interesting questions are raised by the results obtained 

 with the White Emmer, Russian Emmer, and Common Emmer, 

 and also with the rye-wheat hybrid. These three Emmers are 

 mildew-resistant varieties of Triticiim dicoccum^ two other varieties 

 of this species (Black Winter Emmer and Red Emmer) proving 

 quite susceptible to wheat mildew. The rye-wheat hybrid is the 

 offspring of two parents, both of which are extremely susceptible 

 to a particular mildew and also perfectly resistant to the form 

 specialized on the other plant. The offspring^nherits the resistance 

 of both plants, and consequently cannot be fully infected by the 

 fungus specialized on either the rye or the wheat. As has already 

 been stated, the resistance of the hybrid to the wheat mildew is 

 much more marked than is its resistance to the rye mildew. 



Considerable interest has recently been manifested in breeding 

 plants resistant to fungus-diseases. In general, two methods have 

 been followed.* The seed of certain individual plants, which had 

 proved able to withstand the attacks of the particular disease, is 

 collected and used as a starting point for securing a disease-resis- 

 tant variety. The other method has been to cross varieties that 

 have been found to be resistant, with susceptible varieties, in order 

 to combine in one type the resistant characters of the one with the 

 productivity, adaptability for market, etc., of the other. 



The first method has been followed by Blinn ^ in developing 

 cantaloups resistant to a blight caused by Macrosporiiim ciiciivi- 

 erimwi EUis & Everhart ; by Bolley ^ in securing flax resistant 

 to flax wilt {Fiisariiim Lint Bolley); by Bain and Essary^ in 



*For a more complete account of these methods, see a paper by the writer in the 

 Second Annual Report of the State Board of Horticulture of Missouri, 284-286. 

 1909, 



