CHAPTER IX 



SOME RESULTS OF SELECTION WITH SELF- 

 FERTILIZED CROPS 



In its broadest sense, selection is really at the basis of all animal 

 or plant improvement by breeding. Evidence accumulated by 

 early plant breeders indicated to them that selection of the most 

 desirable plants for seed was highly profitable, irrespective of 

 whether the plants were naturally cross-fertilized or self-fertil- 

 ized. Darwin believed that the mean type of any population 

 could be changed by a plus or minus selection. It was left for 

 Johannsen (1903) to point out the true significance of selection 

 within a naturally self -fertilized crop. 



Before discussing Johannsen 's pure-line concept and its rela- 

 tion to the improvement of self-fertilized crops by selection, a 

 brief survey of early work on improvement of naturally self- 

 fertilized cereals is desirable. 



EARLY INVESTIGATORS IN SELECTION OF SELF-FERTILIZED 



CEREALS 



John Le Couteur and Patrick Shirreff were first to use the prog- 

 eny test in making selections. The former did considerable 

 work with wheat. In the early part of the nineteenth century 

 he grew what he supposed to be a uniform variety. Professor 

 La Gasca, of the University of Madrid, upon inspecting Le Cou- 

 teur 's wheat in the field pointed out no less than 23 distinct 

 forms. This observation led the latter to make a collection of 

 150 varieties. Le Couteur simply took it for granted that the 

 progeny of any one individual would breed true. Patrick 

 Shirreff, another breeder of cereals, who lived in the middle of the 

 nineteenth century, worked along somewhat different lines. He 

 searched for the exceptional plant to start a new variety, and 

 discovered seven such varieties. 



Frederic F. Hallett also followed rigid selection of individual 

 plants in his wheat breeding. Furthermore, he proceeded on the 

 theory that the selection of the best spike on the plant and the 



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