:384 Reed: The mildews of cereals 



securing red clover resistant to Colletotrichum Trifolii Bain ; by 

 Jones ^^ and others in securing potatoes resistant to late blight 

 \Phytophthora infcstans de Bary) ; and by Orton ^^ in securing 

 cowpeas resistant to the wilt fungus \Neocosmospora vasinfecta 



{Atk.) E. F. Smith]. 



A great deal has been done toward securing rust-resistant 

 -varieties of wheat and other cereals. For this purpose Carleton ^ 

 has introduced into this country a number of foreign wheats, 

 especially Russian varieties. The common bread wheats, varieties 

 of Tritiann vulgare, in general are quite susceptible to attacks of 



rust. On the other hand, many durum wheats, varieties of Tnti- 

 <:uni durum, are relatively immune, the variety lumillo being 

 almost perfectly resistant. During the season of 1904,^ the loss 

 of common wheats in large areas of North Dakota, South Dakota, 

 and Minnesota amounted to 50-60 per, cent, of the crop. In the 

 case of the durum wheats, the loss was 10 per cent, or less, 

 generally 3-5 per cent. 



Einkorn ( TriticuJn vwnococcum) is also very rust-resistant. 

 Some varieties of Emmer [Triticum dicocawi) are resistant, while 

 others are susceptible. The Spelts {Triticum Speltd) are quite sus- 

 ceptible to rust attacks. 



The second method, that of crossing susceptible and resistant 

 varieties, has also been followed. The wilt disease already mentioned 

 is extremely destructive to watermelons ; the citron, however, is 

 resistant. Orton^^ has obtained a hybrid between the watermelon 

 and the citron which is resistant to the wilt. Unfortunately, how- 

 ever, the melons produced on the hybrid vines were not edible. 

 The hybrid was again crossed with the watermelon and plants 

 obtained, one-fourth citron and three-fourths watermelon, very re- 

 sistant to wilt and also producing good, edible melons. 



Attempts have been made to cross resistant varieties of cereals 

 with non-resistant with a fair degree of success. Especially in- 

 teresting are the results obtained recently by Biffen,^' * He has at- 

 tempted to show that Mendel's laws of inheritance apply to the 

 transmission of disease-resistant qualities. In 1902 Rivet wheat 

 {Triticum fur^iihm) and Red King {Triticum vu!^iire)vjer& crossed. 

 The former is relatively immune to the attacks of the yellow rust 

 {Puccinia Glumaruvi), while the latter is very susceptible. The 



