EXCHANGING AND CONSERVING TREE BREEDING MATERIALS 



Robert Z. Callaham 

 Forest Service, U. S. Department of Agriculture 3 

 Washington, D. C 3 U.S.A. 



.ABSTRACT 



Breeding for rust resistance, as for any other characteristic 

 requires access to a variety of genetic materials. Interna- 

 tional cooperation is needed in the exchange and conservation 

 of germ plasm of forest trees. Problems of the breeder in 

 obtaining the plant material he requires are numerous. Inter- 

 national organizations helpful in overcoming these obstacles 

 include the Food and Agriculture Organization of the United 

 Nations, the International Union of Forestry Research 

 Organizations and others. Examples of National efforts that 

 have contributed to meeting the needs of forest tree breeders 

 are given. The lesser need for conservation of germ plasm in 

 forestry than in agriculture is explained. Some tree species 

 in danger of extinction or of genetic change are listed, and 

 the need for conservation of others is discussed. 



INTRODUCTION 



To breed for rust resistance or any other characteristic of a high- 

 yielding variety of trees, the breeder must have access to a great 

 variety of genetic materials. These include not only the varieties and 

 provenances of the species with which he is primarily concerned, but also 

 the related species from which desirable traits might be introduced. Of 

 equal importance are non-related species having desired traits, like rust 

 resistance. These might be introduced as exotics where rusts or other 

 pests limit the growth of native species. Acquiring these diverse 

 genetic materials is essential to the success of most breeding programs. 



In recent years, several meetings have stimulated interest and led 

 to improvement in our institutions and procedures for exchanging and 

 conserving germ plasm of forest trees. This paper relates to the inter- 

 national aspects of this activity. 



International movement of materials for forest tree breeding has 

 accelerated rapidly in recent years as tree breeding programs have 

 expanded. Breeders recognize the importance of exchanging material. 

 They make extensive use of many species, provenances and selections in 

 their breeding to produce high-yielding varieties. Breeders are con- 

 cerned not only with resistance to rust or other pests but also with 

 other desirable traits. They seek rapid growth, good form and superior 

 wood qualities to name a few. 



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