Methods of Utilizing Induced Mutation in 

 Crop Improvement 



JAMES MacKEY 

 Swedish Seed Association, Svalof, Sweden 



Thirty years of applied mutation work have gradually sapped 

 the first pessimistic idea that induced mutations represent only 

 the deleterious types of spontaneous mutation. More and more, genet- 

 icists have become convinced that the fundamental evolutionary 

 force, the creation of variability, can now be controlled by man. 

 From our present knowledge, it seems theoretically not too incon- 

 siderate to accept ideas like the one held by Gaul (26, p. 276), x when 

 he says, "Today there is little doubt that all the genes involved in the 

 world collections of our cutlivated plants can be reproduced by 

 induced mutations". But theory is one thing and practical plant 

 breeding; another. For that reason, it is still a debate, but it is now 

 less concerned with whether the imitation is possible or not than 

 with whether it is economical or not. 



Proper economical evaluations need more evidence and experi- 

 ence than does a statement of purely academic significance. However, 

 since plant breeding is nothing more than controlled and directed 

 evolution, I think it is easier for us to make the correct evaluation if 

 we always keep the theoretical aspects in mind. If we compare with 

 nature, I have no feeling that we use the two evolutionary forces, 

 recombination and selection, in a different way in our plant breeding. 



Can we today make the same statement in connection with the 

 third force, mutation? I do not think so, unless we accept such an 

 extreme idea that macromutations are of overwhelming importance 

 and are independent of background genotype. Most of our evidence 

 that mutation breeding is a reality is based on distinct off-types either 

 from a morphological or from a physiological standpoint, and these 

 off-types have mostly been evaluated as raw mutants. It is logical first 

 to build up proof in this way, since a macromutation in a self- 

 fertilized crop plant can be made to constitute absolute evidence of 



a See References, page 354. 



336 



