30 percent) or from the surviving trees within stands that have had high mortality 

 due to blister rust (level of resistance 10-15 percent). 



Shelterwood or seed trees of white pine that have survived the epidemic could be 

 left to regenerate a prepared site. In many stands (60-80 years old) mortality of 

 white pine by blister rust is 90 percent. Nonetheless, there are usually 20-30 

 living trees per acre that survive. l\Tien such a stand is cut or salvaged, several of 

 these trees can be left to provide seed for regeneration. According to our data 

 about 20 percent of the seedlings will be resistant under nursery conditions (Hoff 

 and others 1976) . 



Besides regenerating a stand, this approach has other benefits. In contrast to 

 artificial selection, nature selects for all mechanisms of resistance. Man selects 

 for only those he can see. Also, nature uses all races of blister rust over the many 

 inoculation years. Man uses only those he collects and usually only once for each 

 progeny test. 



PUBLICATIONS CITED 



Bingham, R. T. 



1972. Artificial inoculation of large numbers of Pinus monticola seedlings with 

 Cronartium ribicola . In: Biology of rust resistance in forest trees, p. 357-372. 

 USDA For. Serv. Misc. Publ. 1221, 681 p. 



Bingham, R. T., R. J. Hoff, and G. 1. McDonald. 



1971. Disease resistance in forest trees. Annu. Rev. Phytopathol. 9:433-452. 

 Bingham, R. T., R. J. Hoff, and G. I. McDonald. 



1973, Breeding blister rust resistant western white pine. VI. First results 

 from field testing of resistant planting stock, USDA For, SeT\r . Res. Note 

 INT-179, 12 p. Intermt. For. and Range Exp. Sta. , Ogden, Utah, 



Bingham, R. T. , R. J. Olson, W. A. Becker, and M. A. Marsden. 



1969. Breeding blister rust resistant western white pine. V. Estimates of 

 heritability, combining ability, and genetic advance based on tester matings. 

 Silvae Genet. 18:28-38. 

 Hanson, C. H, , T, H. Busbice, R. R. Hill, Jr., 0. J. Hunt, and A. J. Oakes. 



1972. Directed mass selection for developing multiple pest resistance and 

 conserving germ plasma in alfalfa. J. Environ. Qual . 1:106-111. 



Harlan, J. R. 



1976. Diseases as a factor in plant evolution. .Annu. Rev, Phytopathol. 14:31-49. 

 Hoff, R. J., and G. I. McDonald. 



1971. Resistance to Cronartium ribicola in Pinus monticola: short shoot fungicidal 

 reaction. Can. J. Bot. 49:1235-1239. 



Hoff, R. J., and G. I. McDonald. 



1972. Resistance of Pinus armandii to Cronartium ribicola. Can. J. For. Res. 

 2:303-307. 



Hoff, R. J., and G. I. McDonald. 



In press. Resistance to Cronartium ribicola in Pinus monticola: reduced needle 

 lesion frequency. Can. J. Bot. 

 Hoff, R. J., G. I. McDonald, and R, T. Bingham. 



1973. Resistance to Cronartium ribicola in Pinus monticola: structure and gain 

 of resistance in the second generation. USDA For, Serv. Res. Note INT-178, 



8 p, Intermt. For. and Range Exp. Stn. , Ogden, Utah. 

 Hoff, R. J., G. I. McDonald, and R. T. Bingham, 



1976, Mass selection for blister rust resistance: a method for natural regeneration 

 of western white pine. USDA For. Serv. Res. Note INT-202, 11 p. Intermt. For. 

 and Range Exp. Stn., Ogden, Utah. 



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