292 MUTATION AND PLANT BREEDING 



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Comments 



Caldecott: You have indicated that you obtain as many mutants from 

 acute irradiation as from chronic irradiation. If this is true, does the 

 gamma field still serve a useful purpose in a plant breeding program — 

 note a plant breeding program, not a basic research program? 



Nybom: I think we know still too little to distinguish between a muta- 

 tion breeding program and a basic research program. Certainly more 

 studies are required to elucidate the different effects of chronic and acute 

 irradiations, irradiations at different stages, etc. Also, for the irradia- 

 tion of bulky objects, like fruit trees and others, a gamma source seems 

 to be a most suitable tool, so I do not think such a source can be said 

 to be out-of-date. 



