50 BIOLOGICAL EFFECTS OF ATOMIC RADIATION 



IV. Evaluation of Research 



In the United States, agricultural research is primarily supported by public funds, fed- 

 eral and state. In seeking examples of the returns from public expenditures which are in excess 

 of 230 million dollars annually, attempts are sometimes made to put a dollar value on this or 

 that item of expenditure or research, or this or that improvement arising from research. 

 Sometimes this is relatively easy, as for example, when a wholly new product is involved. 

 More often it is not possible because new knowledge does not stand alone but is incorporated 

 in the previous structure. Much of the work involving radioisotopes and tracer techniques in 

 agricultural research falls in this category. Advances, specifically aided or catalyzed through 

 adoption of such techniques, can rarely be so clearly delineated that assessment in increased 

 dollar income or improved production efficiency is feasible. 



v. Radiation and Plant Mutation 



In our earlier report we discussed at some length the use of radiation to induce mutants 

 in plants and micro-organisms and the exploitation of this phenomenon in crop breeding pro- 

 grams. It was our considered opinion that while this placed a new tool in the hands of plant 

 breeders, agronomically desirable new varieties are not likely to emerge by irradiation only, 

 and that "mutation breeding" will not displace but will supplement the more conventional 

 programs soundly based on known genetic principles. So far, very few new varieties of crop 

 plants developed from radiation-induced mutants have in fact been released and accepted 

 for wide planting by farmers. In general, the search to date has been concentrated on mutants 

 having exceptional disease resistance, earliness, or, in cereals, strength of straw, because these 

 are characteristics which are readily recognizable and urgently needed. The modification of 

 other characteristics, perhaps less easily detected, may have greater potential in the long run. 



Among microbiologists, radiation is becoming accepted as a routine means of inducing 

 mutants of micro-organisms possessing different biochemical capabilities. Radiation tech- 

 niques with this objective therefore find use in industrial microbiology on the one hand, and in 

 basic studies of the metabolism and genetics of micro-organisms on the other. 



VI. Radioisotopes for Physiological Research 



Irradiation methods are not likely to be helpful in the genetic improvement of farm 

 animals, except possibly with poultry, but substantial use of radioisotopes is being made in 

 the investigation of problems of animal physiology and nutrition. We drew attention earlier 

 to the research limitations presented by the problem of disposal of larger farm animals after 

 use in experiments involving radioisotopes. Even when short half-life isotopes were used at 

 tracer levels, the animals could not be marketed through the usual outlets. The Meat Inspec- 

 tion Division of the Agricultural Research Service, U. S. Department of Agriculture, after 

 consultation with the Food and Drug Administration, has now established and published pro- 

 cedures for determining the acceptability of meat from animals which have been treated with 

 tracer levels of radioactive isotopes for experimental purposes. The public welfare is fully 

 protected in this measure. 



