PLANT BREEDING 415 



381. Wheat breeding: its purpose. Wheat is the most im- 

 portant grain for human food in temperate climates, and North 

 America is by far the greatest wheat-producing region in the 

 world. The annual value of the crop of the United States 

 ranges from $250,000,000 to 1500,000,000. Scientific wheat 

 breeding began hardly a century ago, and has progressed 

 more in the United States since 1890 than during all our 

 previous history. 



Some desirable qualities to be sought in wheat breeding are 

 (1) large yield per acre ; (2) good quality for bread making, 

 requiring a high per cent of the tenacious gluten, the main 

 protein portion of the grain ; (3) hardiness, shown in winter 

 wheat, in resisting severe winter conditions ; (4) resistance to 

 rust ; (5) resistance to drought. 



Not all of these qualities can be combined in the highest 

 degree in any one variety, and therefore every region should 

 grow the particular kind of wheat best suited to the local 

 conditions and market. 



382. Wheac breeding : the method. In order to show how 

 carefully the process of wheat breeding is managed in our best 

 agricultural experiment stations, the principal steps of the 

 operation are here given in the barest outline, omitting many 

 most important details. 1 



(1) Ten thousand large, sounu kernels of a single good 

 variety of wheat are selected, planted in hills, and each hill 

 numbered. About 95 per cent of the poorer plants are re- 

 jected as they mature. The heads of each of the chosen plants 

 are put together in an envelope and preserved. When thor- 

 oughly dry the product of each plant is weighed, and only a 

 few of the heaviest groups of heads are kept for seed. 



(2) The second year about a hundred of the seeds of each 

 mother plant are planted in a group to which is given a special 

 designating number (hundred-group or centgener). Heads of 



1 See Bulletin 62, University of Minnesota Agricultural Experiment 

 Station, and Bulletin 29, Division of Vegetable Physiology and Pathology, 

 U. S. Dept. Agr. 



