SELECTION WITHOUT ARTIFICIAL CROSSING. 



35 



INDIVIDUAL SELECTION. 



In the form known as individual selection we start with superior 

 plants and keep their seeds separate. This enables us very quickly 

 to determine which of the original selections are superior under a 

 wide range of conditions, so that within a few years we can determine 

 which of our original selections represent the best strains in the 

 variety. Then by propagating from them and by continuously 

 selecting to avoid saying any plants which may be deteriorating 

 from hereditary characters becoming latent, we can maintain the 

 variety at a high standard. But it must be remembered that we 

 can not increase the superiority of a pure strain by selection except 

 in those comparatively rare cases where characters that were latent 

 in our original selection change in their tendency to develop and 

 happen to increase the superiority of the strain. 



That latent characters may reappear in a variety is shown by the 

 following facts. Sometimes, in varieties of potatoes having white 

 skin, tubers are found which have purplish or red skin, at least over 

 part of the surface, and especially about the eyes. Bud sports 

 sometimes exhibit characters not apparent in the parent stock, but 

 common to other varieties of the species. In Doctor Nilsson's 

 work at Svalof, Sweden, black or yellow oats occur at wide intervals 

 in white varieties. All these facts indicate that latent characters 

 occasionally become patent. 



We have already referred to the effect of mass selection on barley 

 at the Ontario Agricultural Experiment Station. Professor Zavitz 

 has also used individual selection on varieties of this crop. In 1903 

 he selected 9,972 grains of the Mandscheuri barley and planted them 

 individually. Seed of 33 of these were planted separately in 1904. 

 By 1908 all but three of these strains had been discarded. One of 

 these, known as ^'O. A.C. No. 21, "which outyields the original variety, 

 is now rapidly replacing the latter on Ontario farms. 



The selection at the Minnesota station, begun by Prof. Willet M. 

 Hays, is individual selection. The seed of each plant, to serve as 

 the original parent of a strain, is saved separately, so that the yield- 

 ing power of pure strains is determined by several years' test of 

 successive generations of their self -pollinating progeny. The best 

 of these are finally brought into culture. This method enables the 

 breeder to secure the best strains present in the seed with which he 

 starts, or, as Professor Hays puts it, it enables the breeder to find 

 those plants having the highest ''centgener" power; that is, the 

 power of producing strains with maximum yields under the widest 

 range of environmental conditions. Some of the wheats obtained 

 in this manner at the Minnesota station have proved decidedly 

 superior to the original mixed stock from which they were isolated. 



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