GAUL: INDUCED MUTANTS IN SEED-PROPAGATED SPECIES 217 



of theoretical mutation experiments. This also holds true for our 

 mutant of Haisa II (Table 3), which was selected from a theoreti- 

 cal experiment described elsewhere (26). Haisa II was marketed 

 in 1950 and used to be one of the most extensively grown varie- 

 ties in Western Germany. However, in recent years, it has con- 

 tinuously lost acreage. The mutants investigated by Scholz (93 and 

 personal communication) belong to "fairly old" varieties, and most 

 of those recorded in Table 3 have now reached the same level of 

 yield as the present top varieties in that area of Germany. 



Scholz (96) also gave an example showing that the yield of 

 mutants can be raised in a second radiation cycle. A barley mutant 

 with naked kernels (2) proved to possess a yielding capacity of 

 90 to 91 per cent as compared with the mother variety Haisa, which 

 has been established in yield trials over a period of 7 years. Because 

 the glumes contribute about 10 per cent of the total kernel weight, 

 the mutant reached the level of the mother variety in terms of "net 

 yield". Irradiation of this mutant resulted in a new mutant which 

 yielded 98 per cent of Haisa on an average of 4 years of testing and 

 which, in addition, is 7 to 8 days earlier. Thus, the net yield of the 

 new mutant has been raised beyond that of Haisa. 



A few years ago the first varieties derived by propagation of 

 a mutant were marketed. In Middle Germany the winter barley 

 Jutta was released, which is derived from an induced mutant in the 

 variety Kleinwanzlebener Mittelfruhe. In this mutant winterhardi- 

 ness, strawstiffness, and yield are improved. At present this mutant 

 covers about 10 per cent of the total acreage of winter barley (125 

 and personal communication). In Sweden a barley erectoides 

 mutant, named Pallas, and a pea mutant, called Weibulls original 

 Stralart, are grown (8). Earlier a new variety of oil rape and another 

 of white mustard were marketed, which were selected from X-rayed 

 material. However, both these species are cross-pollinating and there 

 is no clear evidence that the new varieties originated by mutations. 



Use of Mutants in Cross-breeding 



Information about the use of mutants in cross-breeding is still 

 more limited than that of mutation breeding proper. If characters 

 of two mutants belonging to the same variety are to be combined, 

 a small number of F 2 plants is sufficient. The breeding procedure 



