Pazc 6 



BETTER FRUIT 



March, 192 1 



"Pedigreed" Trees -Where Do We Stand? 



By A. E. Murneek, Assistant Professor of Horticultural Research, Oregon Experiment Station 



(Continued from February Number.) 



THERE is no limit to the number of 

 fluctuating variations. All charac- 

 ters of the tree and fruit are subject 

 to fluctuations. It is one of the means of 

 adjustment of the organism to gross 

 changes of the environment. It may 

 sometimes express itself, in extensive 

 regional variations or fluctuations of 

 one or more characters of a variety. 

 The eastern varieties of apples, for in- 

 stance, when grown in the west as- 

 sume a different, generally more oblong 

 form. The soil, atmospheric conditions, 

 cultural practices, such as priming, fer- 

 tilization, spraying, irrigation, may 

 cause marked fluctuations from the 

 average of trees in a whole region, an 

 orchard, the individual tree, or only a 

 part of the tree. Most probably the ef- 

 fect of food supply would be of prime 

 importance as a factor causing fluctu- 

 ations. Thomas A. Knight, the eminent 

 English horticulturist, recognized this 

 fact when he said that "Nutrition reigns 

 supreme in the whole realm of variabil- 

 ity." So, too, Darwin was of the opin- 

 ion that "of all the causes which in- 

 duce variability, excess of food is prob- 

 ably the most powerful." The com- 

 plexity of the situation becomes at once 

 evident when we consider that fre- 

 quently more than one and often all of 

 the factors enumerated above may be 

 the direct or indirect causes of this 

 type of variations. Moreover, it may 

 exhibit itself in varying and changing 

 degrees. 



Fluctuating variations as a rule are 

 extremely seldom if ever inherited, that 

 is, they may not be perpetuated either 

 sexually through the seed or asexually 

 through cuttings or buds. Any attempt 

 to propagate by means of buds, a tree 

 that is bearing particularly heavy crops, 

 or well formed or highly colored fruit, 

 if these characteristics have been 

 brought about and maintained by fa- 

 vorable environmental conditions and 

 hence are of a fluctuating nature, would 

 be of no avail. Neither the output of 

 an orchard nor a particular strain or 

 characteristic of the variety may be ac- 

 centuated or established by this prac- 

 tice. For the sake of emphasis may it 

 be repeated once more that such vari- 

 ations or fluctuations are not trans- 

 missible. 



This permits us to explain why bud 

 selection experiments of the agricul- 

 tural experiment stations, as stated 

 previously, have given almost invari- 

 ably negative results. As an example, 

 trees propagated from heavy and light 

 bearing Ben Davis at the Missouri Agri- 

 cultural Experiment Station did not 

 come true to the parent plants— the 

 bearing habit was not transmitted. 

 Likewise strawberries propagated by 

 means of runners (buds) for ten gen- 

 erations at this station, gave the same 

 results— the offsprings from high yield- 

 ing plants were no nunc: productive 

 than those from parents with a low 

 record of hearing. Moreover the vari- 

 ations exhibited by the two would-be 



strains were just as great as in the orig- 

 inal stock. Similar negative results 

 with strawberry selection have been re- 

 ported from other stations. 



Recently a full account has been pub- 

 lished of exhaustive apple-bud selection 

 investigations of the University of Illi- 

 nois Agricultural Experiment Station. 

 Buds from twenty-one varieties were 

 used in connection with this work. 

 They were chosen in regard to their 

 size and location on the tree. It was 

 found most conclusively that, for pur- 

 poses of propagation, there is no dif- 

 ference between buds of large and 

 those of small size. Neither does it 

 make any difference from what part of 

 the tree the buds are taken. 



So much for fluctuations. Another 

 type of bud variation is, however, not 

 infrequently exhibited by plants. It 

 differs most distinctly from ordinary 

 modifications or fluctuations, though a 

 strict line between the two is often dif- 

 ficult to draw. In horticultural litera- 

 ture variations of this character are 

 known as "bud segregation," "vegeta- 

 tive mutation," "bud sports," or simply 

 "mutations" or "sports." For the sake 

 of clearness and brevity let us call this 

 type of variations true "variations" or 

 "mutations." In cases of mutations the 

 internal or genetic constitution of the 

 bud has changed. The "blood" of the 

 tree or branch is different, the external 

 environment, the orchard practices, 

 having very little, if anything, to do 

 with this striking and permanent 

 change in the plant. May it be remem- 

 bered here that fluctuating variations 

 on the contrary are caused solely by 

 environmental differences. 



A word as to the frequency of bud 

 mutations. In Coleus, a greenhouse 

 plant, it has been found that one true 

 but variant may occur in from 500 to 

 20,000 normal buds. While in cases of 

 other plants, like the potato or tobacco, 

 it may be as rare as one in 200,000 



plants. It is not known how often bud 

 variations are exhibited by deciduous 

 trees, the apple for instance. We can 

 assume, however, that they may be as 

 infrequent as in the instances cited. 

 Dorsey tabulated the parentage records 

 of 2,0fi4 leading varieties of apples, 

 cherries, grapes and plums and found 

 only five cases of origin from true bud 

 variations ("sports"). 



Bud mutants are of the greatest im- 

 portance to both horticultural science 

 and practice, for (1) they are often in- 

 herited and hence are transmissible by 

 seeds and (2) in most instances they 

 may be established and propagated by 

 vegetative means, such as cuttings, 

 grafts, buds, etc. This type of vari- 

 ation or mutation may establish a strain 

 or a new variety and may increase the 

 output of the orchard, if the mutation 

 is in the direction of greater fruitful- 

 ness. 



A large number of instances of true 

 bud variations or mutations have been 

 recorded, only a few of which may be 

 mentioned here. Beach has described 

 and named a deep-colored 20-ounce ap- 

 ple, which has been propagated asex- 

 ually and is now known as Collamer. 

 The heavy bearing Paragon is supposed 

 to be a bud sport of Mammoth Black • 

 Twig. Kraus discovered a striped 

 branch of Bartlett pear. It bears striped 

 fruit and shows unmistakably the char- 

 acteristics of a bud mutant. Yellow 

 plums have given rise to fruit of red 

 color. Purple grapes have produced 

 green fruit. Shamel has described a 

 new variety of the French prune, the 

 Coates, which originated as a bud sport 

 on the Petite. The existence of several 

 distinct strains of Italian prunes has 

 been mentioned. The nectarine orig- 

 inated as a bud sport on the peach. 

 Many more instances of true bud vari- 

 ations resulting in increased size — or 

 in differences in the form of the fruit 

 could be cited. So, too, the time of 



Figure 1. Apple trees are bench grafted before Ihej are set out in the nurserj ro 



