200 



BREEDING CROP PLANTS 



system of broad breeding, the use of a high-yielding, adapted 

 variety, and the storage of the seed so that it will germinate 

 vigorously are important practices which should be a part of each 

 corn-breeder's plan. 



Relation between Heterozygosis and Vigor. In an earlier 

 chapter the effects of self-fertilization in corn were discussed 



FIG. 45. Minn. No. 13 self-fertilized high protein strain No. 1. This strain has 

 dark green leaves, medium sized ears and the tassels are somewhat scantily pro- 

 vided with pollen. 



and the hypothesis outlined that vigor in FI crosses was due to 

 the partial dominance of linked growth factors. This question is 

 of considerable importance from the standpoint of the corn 

 breeder. The subject will be discussed under the following 

 headings: 



