CLONAL ROOTSTOCKS FOR THE APPLE 3 



orchardist who hopes to avoid poor trees in the orchard by the use of clonal stocks 

 is likely to be disappointed. He may gain a little in uniformity but not much. 



Clonal Rootstocks 



Clonal rootstocks have been known for 200 years or more though they have 

 never been used extensively. The objective has been the production of dwarf 

 trees. A clonal rootstock may be considered to be a variety just as Mcintosh is 

 a variety. Both originated from single seedling trees and are propagated by 

 asexual means such as budding, grafting, layering, or by cuttings; neither comes 

 true from seeds. All individuals of a variety are genetically alike except in rare 

 cases where a mutation or bud sport appears; practically all differences between 

 individual trees are due to environmental influences. 



The difference between clonal rootstocks and varieties is that varieties have 

 been chosen because of superior fruit and tree characters which make them desir- 

 able for fruit production, while no attention is paid to fruit characters when 

 selecting clonal rootstocks; they are chosen because they can be propagated 

 readily by asexual means and for their effect on the varieties budded on them. 

 It is possible that a good clonal rootstock or a good variety may appear in any 

 lot of apple seedlings but in only an exceedingly small percentage. 



The selection and propagation of clonal rootstocks has been going on in Europe 

 for many years. The importation of these rootstocks to America began many 

 years ago. About a dozen different kinds were known, but little was published 

 about the different kinds and most of them were unknown in America. In 1912, 

 Wellington of the East Mailing Research Station in Kent, England, collected 

 clonal stocks from stock growers in England and on the Continent for the purpose 

 of studying them and their value as apple rootstocks. They were received under 

 various names. It became apparent at once that the situation was very confused 

 as to names and types. Many lots consisted of mixtures of two or more stocks, 

 Wellington and his successor, Hatton, separated the various stocks, designated 

 them by numbers and applied the proper names so far as they could be ascer- 

 tained. Hatton and his co-workers at East Mailing have, during the past 25 

 years, given much study to these stocks and their interrelations with English 

 varieties of apples. Several American Experiment Stations and the United 

 States Department of Agriculture have imported these stocks. The Massachu- 

 setts Station secured 16 of them in 1926 and has since added others and propa- 

 gated them by layers, nurse-root grafts, and root cuttings and used them as 

 rootstocks on which to bud our varieties. 



These rootstocks are known in this country b}^ their Mailing numbers rather 

 than by names. Some of them have proved to be dwarfing stocks, but others 

 have little or no dwarfing effect. The numbers and names, so far as given, of the 

 stocks in the nurseries of the Massachusetts Experiment Station are as follows: 



Very dwarfing stocks: Mailing VIII — French Paradise 



IX — Yellow Metz 



Semi-dwarfing stocks: Mailing I — Broad leaved Paradise 



" II — True Doucin 



III — "Hollyleaf" 



" IV — Holstein Doucin, Yellow Doucin 



" V — Improved Doucin 



" VI — Nonesuch Paradise 



" VII — Not named 



