306 MUTATION AND PLANT BREEDING 



3. Hackbarth, Jaochim, and Troll, Hans-Jiirgen. 1959. Lupinen als 



Kornerleguminosen und Futterpflanzen. Hand buck der Pflanzen- 

 ziichtung, 4: 1— 51. Berlin: Verlag Paul. Parey. 



4. Harlan, Jack R. 1956. Distribution and utilization of natural vari- 



ability in cultivated plants. In Genetics in Plant Breeding. Brook- 

 haven Symp. in Biology, No. 9, 191-206. 



5. Hayes, H. K., Immer, F. R., and Smith, D. C. 1955. Methods of Plant 



Breeding. Neiv York: McGraw-Hill Book Co., Inc. Ed. 2. 



6. Myers, W. M. 1960. Some limitations of radiation genetics and plant 



breeding. Indian Jour. Gen. ir Plant Breed., 20: 89-92. 



7. , Ausemus, E. R., Koo, F. K. S., and Hsu, K. J. 1956. Resist- 

 ance to rust induced by ionizing radiations in wheat and oats. 

 Proc. of the Intern. Conf. on the Peaceful Uses of Atomic Energy, 

 Geneva. New York: United Nations, Vol. 12: 60-62. 



8. Vavilov, N. I. 1957. World resources of cereals, grain, leguminous 



crops, and flax and their utilization in plant breeding. In Agroe- 

 cological Survey of the Principal Field Crops. Izdatel stvo Akademii 

 Nauk. SSSR Moskva-Leningrad. (Plant Breed. Abs., 28: 3576. 1958.) 



9. Westergaard, M. 1960. A discussion of mutagenic specificity: 1. 



Specificity on the "geographical" level. Chem. Mutagenese Erwin- 

 Baur-Geddchtnisvorlesungen. I. Abhandlungen der Deutschen 

 Akademie der Wissenschaften zu Berlin, 116-121. 

 10. Whittinghill, Maurice. 1955. Crossover variability and induced cross- 

 ing-over. Symp. on Gen. Recombination, Jour. Cellular and Com- 

 parative Physiol., 45:Suppl. 2, 189-217. 



Comments 



Gaul: If I understood it correctly, you have the feeling that the example 

 of Professor Vettel which I gave might not be representative. Vettel 

 indicated that only 0.3 per cent of his 5,045 F 2 populations resulted in 

 new varieties. You mentioned that professor Hayes needed fewer F 2 popu- 

 lations for the development of new varieties. Such a comparison is, 

 however, very limited because it depends on the breeding procedure. I 

 would like to repeat that Vettel is one of the most successful German 

 breeders. In Europe many breeders prefer to have many F 2 popula- 

 tions and analyze only a few very carefully. If I understand, you at 

 Minnesota did the contrary. You had very few hybrid populations which 

 you analyzed very carefully. Thus, I think that a comparison of Vettel's 

 results and yours is very difficult, if not impossible. 



Myers: I quite agree with Doctor Gaul that a comparison of Doctor 



