CONIFERS VS. CROP PLANTS AS BREEDING MATERIAL 25 



for resistance to white pine blister rust should be on a very broad 

 genetic base. Before proceeding with this summary, I will try to explain 

 what I mean by breadth in this instance. This is simply the inclusion of 

 a very large number of resistant candidate trees in the base population 

 to cover the diversity of ecotypes in the white pine regions and to 

 select within these ecotypes a large number of phenotypes with good growth 

 and quality characteristics. The expression "large number" in both cases 

 is left unspecific, but it is intended to indicate a large gene pool as a 

 hedge against development of new pathogen races and the probable invasion 

 of new biotic enemies. 



All this may be interpreted as a large unwieldy tandem selection 

 scheme. I would only suggest that several features of trees as breeding 

 materials make it possible to retain flexibility in adopting breeding 

 strategies. The long life and cloning capacity of trees makes it possible 

 to put genotypes on the shelf for indefinitely long periods . Additional 

 flexibility is provided by the relatively great longevity of pine seed, 

 and the abundance and longevity of pine pollen. The size and durability 

 of trees make them easy to file and recover, provided one has the space. 

 Even the space requirement is not a total liability. It is possible to 

 combine forest production with breeding (Duffield, 1963) because of the 

 space and time extensions of trees which in effect makes each one an 

 easily recognizable individual—even more so than the members of a large 

 animal herd, for trees don't move. 



I hope I have indicated that the resistance breeder working with 

 trees is not critically limited by the nature of his materials. His 

 success, like that of the agricultural plant breeder, depends on the will 

 to get the job done, expressed in financial support and the cooperation of 

 those who use his product. 



LITERATURE CITED 



Bergman, A. 1968. Variation in flowering and its effect on seed cost. 



Norch Carolina State Univ. School of Forest Resources Tech. Report 38. 



63 p. 

 Berry, C. R. , and G. H. Hepting. 1964. Injury to eastern white pine by 



unidentified atmospheric constituents. Forest Sci. 1°: 2-13. 

 Bingham, R. T., R. J. Hoff, and R. J. Steinhoff. In press. Western white 



pine (Pinus montiaola Dougl.) In Genetics of important North American 



forest trees. 

 Bingham, R. T. , and A. E. Squillace. 1958. Localized ecotypic variation 



in western white pine. Forest Sci. 4: 20-34. 

 Daubenmire, R. , and J. B. Daubenmire. 1968. Forest vegetation of eastern 



Washington and northern Idaho. Washington Agr. Exp. Sta. Tech. Bull. 



60. 104 p. 

 Duerr, W. A. 1967. The changing shape of forest resource management. 



J. Forest. 65: 526-529. 

 Duffield, J. W. 1963. Integrating progeny testing with forest production, 



Northwest Sci. 37: 119-125. 

 Hermann, R. K. , and D. P. Lavender. 1968. Early growth of Douglas-fir 



from various altitudes and aspects in southern Oregon. Silvae Genet. 



17: 143-151. 

 Mirov, N. T. 196". The genus Pinus. Ronald Press, New York. 602 p. 



