CHAPTER XXV 

 PLANT-BREEDING METHODS 



In no phase of agriculture is there greater need of scientific planning 

 with reference to economy of time and resources as well as efficiency of 

 method than in plant breeding. In annual species the individual plant is 

 of small intrinsic value as compared with a domestic animal, and gen- 

 erations follow each other in rapid succession. These facts tend to en- 

 courage methods that are wasteful or inefficient, or at any rate methods 

 that fail to accomplish all that might be accomplished in a given time. 

 In work with perennial species the need of a scientifically planned system 

 of breeding is even more urgent because of the greater intrinsic value of 

 the individual plant and the longer time required to obtain results. 



Pedigree Culture Methods. The pedigree culture was first used in 

 a systematic manner by Vilmorin in breeding wheat. Later it was 

 adopted by Hays of Minnesota and by Nilsson in Sweden. The essen- 

 tial feature of the pedigree culture consists in rearing successive gen- 

 erations of organisms under such conditions that the ancestry of each 

 individual is known. Its purpose is to insure absolutely accurate knowl- 

 edge of ancestry. To attain to this ideal many precautions are necessary, 

 and some sources of error, due principally to accident, cannot be entirely 

 eliminated. However the same accident is not liable to happen twice to 

 the same culture and when an accident does occur sometimes the culture 

 can be repeated. Any material whose pedigree is in doubt should be 

 eliminated at once or, if rare or valuable, relegated to the class of unknown 

 until its own behavior in breeding indicates its genotypic nature. 



Seedage methods in pedigree culture work with plants are very im- 

 portant. Handling seeds and seedlings requires quite as much care as 

 does castration and pollination especially with very small seeds and this 

 work should be done by the person in charge if possible. However, 

 the work of transplanting and field planting can usually be performed by 

 a person especially adapted and trained for it. The work of taking 

 notes, collecting seed and recording data, on the other hand, should 

 be done by the investigator or breeder. The original label should be 

 collected with the seed and preserved until the permanent records are 

 made; then it should be carefully copied and compared with the written 

 notes before being discarded. As a rule it is well to count the seeds in 

 each bag inasmuch as hybrid seed may prove to be partially sterile or 

 may exhibit delayed germination or other abnormalities. 



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