A WHITE PINE BLISTER RUST RESISTANCE BREEDING PROJECT 

 IN NORTHEASTERN MINNESOTA 1 



Scott S. Pauley 2 and Clifford E. Ahleren 

 School of Forestry 3 University of Minnesota, St. Paul, Minn, and 

 Quetico-Superior Wilderness Research Center 3 Wilderness 

 Research Foundation, Ely , Minn. , U.S.A., respectively 



.ABSTRACT 



The breeding project here briefly described has been designed 

 primarily for a low budget. The design also makes it feasible 

 to utilize a broad genetic base of selections in the initial 

 phase of the program. 



Phase I consists of the phenotypic (mass) selection of ca. 1,000 

 Pinus strobus mother-trees in the high white pine blister rust 

 {Cronartium ribicold) infection areas of northeastern Minnesota. 

 About 100 plants grown from open-pollinated seed of each of these 

 selections (i.e., ca. 100,000 plants) are being propagated and 

 outpl anted on a high infection site near Tofte, Minnesota, and 

 subjected to a natural screening for rust resistance. 



The surviving plants will be allowed to inter-pollinate and the 

 seed may be used for commercial outplantings . Genetic gain in 

 resistance may be expected to be rather low at this stage, 

 possibly in the order of 12 to 15 percent. 



Flowering by the age of 15 to 20 years in the surviving plants 

 of the screen test will permit initiation of the final recur- 

 rent family selection phases of the improvement program. Total 

 genetic gains in such full-sib family selection may hopefully 

 be expected to range from 30 to 40 percent in the first genera- 

 tion and possibly higher in succeeding generations. 



In spite of a lengthened time schedule, the advantages of this 

 mass selection-screen test phase are: (1) The large number of 

 trees screened will provide a broad genetic base for later 

 improvement of rust resistance and other desirable character- 

 istics, (2) the uniformity of treatment in the screen test 

 makes the possibility of "escapes" lower than in nature, (3) 

 costs of breeding with these trees will be low because of uni- 

 form age, size, and proximity in which they will be growing, 

 and (4) the planting design can be adapted to tests of various 

 techniques such as fertilizers to hasten flowering. 



-.-. cooperative project involving the U. S. Forest Service, Quetico- 

 Superior Wilderness Research Center, and the School of Forestry, 

 University of Minnesota. 



Editor's note: Dr. Pauley's distinguished career in forest genetics 

 ended with his death in April 1970. 



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