BREEDING OATS RESISTANT 

 TO STEM RUST' 



Frkd Griffee- 



Minnesota Agricultural Experiment Station, St. Paul , Minnesota. 



THE use of 

 resistant va- 

 rieties of field 

 crops is being ad- 

 vocated as one of 

 the chief means of 

 disease control. 

 Frequently resis- 

 tance exists in a 

 variety otherwise 

 unimportant- Be- 

 fore it can be fully 

 utilized this resis- 

 tance must be 

 combined with 

 desirable eco- 

 nomic characters 

 from other varie- 

 ties. In case re- 

 sistance is a 

 recessive charac- 

 ter all plants of 

 the desired type 

 are selected in the 

 F2 generation and 

 tested in later 

 generations, since 

 the onlv sure 



means of deter- 

 mining the value of a plant is to grow 

 and examine its progeny. If resistance 

 is dominant, however, it is impossible 

 to distinguish the homozygous from 

 the heterozygous plants in the F2 

 generation, consequently another gen- 

 eration must be grown before selections 

 can be made. 



In the work of breeding cereals for 

 rust resistance at the Minnesota Agri- 

 cultural Experiment Station the purity 



SUSCEPTIBLE AND RUST-RESISTANT 

 OAT LEAVES 



Figure 19. Notice the large blister-like 

 pustules of the rust on the leaf of the suscep- 

 tible variety (Victory), shown on the left. 

 White Russian (center) is a resistant variety; 

 the small, abortive pustules that can be seen 

 develop under extreme epidemic conditions, 

 but appear to do no harm. On the right is 

 shown the leaf of a hybrid between Victory 

 and White Russian oats. All the plants are 

 resistant, which shows that resistant is domi- 

 nant and susceptibility recessive, since the 

 plants of the first hybrid generation show 

 dominant characters only. (See text, p. 188.) 



of F2 plants is 

 determined on the 

 basis of F3 seed- 

 ling tests made in 

 the greenhouse. 

 This work is car- 

 ried on co-opera- 

 tively by the Sec- 

 tion of Plant 

 Breeding of the 

 Divisionof Agron- 

 omy and Farm 

 Management, the 

 Section of Plant 

 Pathology of the 

 Division of Plant 

 Pathology and 

 Botany, and the 

 Office of Cereal 

 Investigations of 

 the United States 

 Department of 

 Agriculture. The 

 method used is 

 well illustrated 

 by the results ob- 

 tained in green- 

 house tests used 



in breeding oats 

 resistant to stem rust, Puccinia grami-- 

 nis avenae Erikes. and Henn. 



In 1921, 600 F2 plants, which ap- 

 peared resistant to rust under an arti- 

 ficially induced field epidemic, were 

 harvested at University Farm. These 

 plants were a part of the progeny of 

 the crosses of White Russian, a variety 

 of oats resistant to stem rust, with Vic- 

 tory and Minota, susceptible varieties. 

 It was reported by Garber^ that in 



1 Published with the approval of the Director as Paper No. 329 of the Journal Series of the 

 Minnesota Agricultural Experiment Station. 



" Acknowledgment is due Dr. H. K. Hayes, Head of the Section of Plant Breeding, Division 

 of Agronomy and Farm Management for suggestions and criticisms. 



3 Garber, R. J., A Preliminary Note on the Inheritance of Rust Resistance in Oats. Jour. 

 Amer. Soc. Agron., XIII:41-43. 1921. 



