Table 4 , --Observed resistance mechanisms in Pinus monticola: Cronartium ribicola 



system 



Mechanism of resistance 



Resistance 

 type 



Hypothesized 

 inheritance 



1. Resistance in secondary needles to a Vertical 

 yellow-spot forming race 



2. Resistance in secondary needles to a Vertical 

 red-spot forming race 



3. Resistance in secondary needles to a Vertical 

 yellow-green-island spot forming race 



4. Resistance in secondary needles to a Vertical 

 red-green-island spot forming race 



5. Resistance in secondary needles that Vertical 

 prevents spot formation 



Reduced frequency of secondary needle 

 infections 



7. Slow fungus growth in secondary needles Horizontal 



8. Premature shedding infected secondary Vertical 

 needles 



9. Fungicidal reaction in short shoot Vertical 



10. Fungicidal reaction in stem Vertical 



11. Slow fungus growth in stem Horizontal 



12. Tolerance to infection Horizontal 



Recessive gene 

 Dominant 

 Dominant gene ? 

 Dominant gene ? 



Horizontal Nondominant gene ? 0.37 



Polygenic 

 Recessive gene 



.46 



Recessive gene 

 Oligogenic ? .367 

 Polygenic ? 0.21-0.46 



SELECTION OF STANDS AND PHENOTYPICALLY RESISTANT TREES 



This base of knowledge has enabled us to recommend a program for the development 

 of resistance in western white pine to blister rust that would have higher stability 

 and genetic diversity. The methods for doing this are the topics of the remainder of 

 this paper. 



Stand Selection 



There are hundreds of stands and thousands of individuals to choose from. A 

 little time spent in the selection of "good" stands can make the program more efficient 

 and very effective. The criteria that we feel are important in selection follows. 



6 



