gaul: induced mutants in seed-propagated species 219 



numerous other properties. In barley, for example, the smooth- 

 awned and naked-kernel mutants of Bandlow (2) are certainly a 

 valuable source for an easy production of top varieties (96). 



An example along this line has already been given by Down 

 and Anderson (17) in bush beans. These authors crossed an earli- 

 ness mutant, induced by X-rays from the variety Michelite, with 

 other strains resistant to Colletotrichum lindemuthianum. The 

 new variety Sanilac, derived from these crosses, combines earliness 

 with resistance and is higher yielding than Michelite. 



A similar case which theoretically deserves still more interest 

 is reported by Stubbe (118) in Antirrhinum. In breeding this orna- 

 mental plant, an erect growth has been desired for a long time. 

 The mutant eramosa approaches that aim and forms usually one 

 culm only. It has almost completely lost the ability of branching 

 and, in addition, it possesses a number of other pathological charac- 

 ters, like inhibition and deformation of the flowers. By crossing 

 eramosa with other varieties, Vogel (according to Stubbe, 118) suc- 

 ceeded in breeding a new nice-looking and vigorous snapdragon 

 which forms only one culm and has normal flowers. Evidently, 

 the undesired pleiotropic by-effects of the mutation have been 

 "dissolved" in a new genetic background. 



This model demonstrates how macro-mutations may be of 

 use in cross-breeding agricultural plants. Little has been done in 

 this field. There are some reports from practical breeders; and 

 though the evidence is not conclusive, two examples may be men- 

 tioned. In barley breeding, the erectoides mutants deserve great 

 interest because of their strawstiffness. However, the dense spike 

 of the mutants is often considered a disadvantage because generally 

 the seed quality is lowered. Thus, the German breeder v. Rosenstiel 

 (84 and personal communication) crossed one of the Swedish erec- 

 toides mutants (ert 12) with other strains of his material carry- 

 ing the mildew-resistance of Hordeum spontaneum, H 204 (86). 

 He selected lines with extremely stiff straw and, in some of them, 

 the dense spike had disappeared. Because these high-yielding lines 

 with a "normal" spike carry also the mildew-resistance of H. spon- 

 taneum, the procedure of v. Rosenstiel is an example of how a char- 

 acter from a wild species and a mutant may be combined. Two of 

 these lines are now in the stage of official yield trials of the Federal 



