THE BREEDING OF CORN 207 



This is probably the quickest way of producing a pure 

 strain of corn. It is accompanied by decreased vigor and 

 yield, the greatest decrease usually taking place the first 

 year of inbreeding. 



254. Value of crossing varieties. — Various breeders 

 have demonstrated that in many cases the immediate 

 effect of crossing two different varieties of corn is the pro- 

 duction of ~a hybrid with greater vigor and higher produc- 

 tivity than either of the parents. It has bebn suggested 

 by Hayes and East ^ that "the production of corn by util- 

 ization of the increased vigor due to a first-generation 

 hybrid, is of commercial importance and is worthy of 

 further trial." In 1892 Morrow and Hunt at the. Illinois 

 Experiment Station gave the results of five tests of the 

 comparative yields of first-generation hybrids and their 

 parents. The table on page 208 gives their results:^ 



255. Method of producing cross-bred seed. — If the 

 farmer or breeder desires to produce each year cross-bred 

 seed for planting purposes the following considerations 

 should be kept in mind in selecting the parent varie- 

 ties: 



(1) The two varieties selected should be of the type 

 ■desired and preferably should have been grown in the same 

 locality for a nimiber of years. 



(2) Better results will be secured if comparatively pure 

 varieties be selected. Investigations on this point indicate 

 that a minimum increase in yield will be secured if the 

 parent varieties are "in a state of hybridity" when 

 crossed. 



(3) Varieties should be selected that mature at the same 

 time. 



1 Conn. Agr. Exp. Sta., Bui. 168, 1911. 



2 111. Agr. Exp. Sta., Bui. 25, 1902. 



