250 BREEDING CROP PLANTS 



radish plants were grown under cover by Riolle and self-fertilized 

 seed was produced in abundance. This led Riolle to suggest 

 that homozygous strains be first produced. These would then 

 furnish material for accurate inheritance studies as well as be of 

 much value for economic breeding purposes. On the other hand, 

 Stout (1920) has stated that there is considerable self -sterility in 

 the cultivated radish. Up to the present, mass selection has been 

 most frequently used as a means of breeding radishes (Tschermak, 

 1916). 



BEETS 



Inheritance and Breeding. Both garden beets and sugar beets 

 belong to the species Beta vulgaris. Kajanus (1913) made a 

 study of the inheritance of root forms in mangels and sugar beets. 

 In general, the F\ roots were intermediate between the parental 

 forms. Sugar beet crosses in which wedge-shaped forms were 

 involved proved to be exceptions. Wedge-shape was completely 

 dominant over walnut-form and also over long, somewhat slender 

 roots (post-shape). The other beet shapes studied were oval and 

 round. Most of the ratios obtained in F z could be satisfactorily 

 explained on the basis of four factors two involving length of 

 root and two concerned with form. 



A marked increase in the sugar content of the sugar beet 

 was produced by Vilmorin through the application of the progeny 

 test method (see page 119). There is some difference of opinion 

 regarding the ease of producing self -fertilized seed. Shaw (1915) 

 demonstrated that the sugar beet, isolated (two miles from any 

 other beet plants), will set some seed. To what extent self- 

 sterility is a factor is unknown. The production of homozygous 

 forms through self-fertilization would seem worth trying as a 

 means of obtaining homozygous material for breeding studies. 

 This method seems a logical procedure for all vegetables which 

 are naturally cross-fertilized but which also set seed freely under 

 conditions of self-fertilization. 



Mass selection is often used in breeding beets. Only those 

 roots which come up to an adopted standard are stored over 

 winter and set out the following spring to become the seed- 

 producing plants. Carrots and parsnips, when bred by mass 

 selection, are handled in a similar manner. Although varieties 

 of any one of the crops, beets, carrots, or parsnips, freely inter- 

 cross, there is no crossing between the three different kinds of 



