CHAPTER XXIII 

 BUD SELECTION 



The efficacy and practicability of bud selection is a subject of con- 

 siderable interest especially among horticulturists. During the past de- 

 cade it has received more and more attention from investigators until now 

 there are under way a number of comprehensive projects which, in future 

 years, should furnish definite information concerning the more important 

 vegetatively propagated crop plants. If it is determined that bud selec- 

 tion is an effective method of improving certain varieties either by secur- 

 ing increased yield or by the discovery of superior strains, its importance 

 to horticulture will have been demonstrated. It will still remain for 

 horticulturists to decide as to the practicability of introducing systematic 

 bud selection in the commercial propagation of those plants in which it 

 has been proved to be an effective method of improvement. The efficacy 

 of bud selection depends upon the nature of bud variation. 



Bud Variation in Plants. There are two kinds of bud variations, 

 viz., modifications and mutations. Modifications are common to all 

 plants and are easily detected even in dormant buds. On deciduous trees, 

 for example, the buds formed during one season's growth usually show 

 considerable variation in size. Such variations do not necessarily repre- 

 sent inherent differences between the buds. They are usually due to 

 differences in the particular combinations of conditions which exist during 

 development of the buds. Phytomers exhibit fluctuating modifications 

 in all other characters as well as size in response to the varying con- 

 ditions of nourishment, light, temperature and other elements of the 

 environment. These modifications are not transmissible and selection 

 of such bud variations alone could never change the average output of 

 an orchard or establish an improved strain. 



Bud mutations, on the other hand, although comparatively rare, are 

 of general occurrence and the new characters induced by them are trans- 

 missible. Hence in considering the efficacy and practicability of bud 

 selection in a horticultural variety the first thing to be determined is the 

 nature and frequency of somatic mutations in that variety. There is 

 only one way in which this question can be answered completely and 

 definitely and that is by extensive tests of vegetatively propagated off- 

 spring. Such tests must be made under controlled conditions especially 

 as regards the nature of the rootstock on which the tested scions are pro- 

 25 385 



