5. Red needle spots, normal size; rust fungus with very high virulence 

 (observed in Oregon, Region 6, USDA Forest Service, blister rust program). 



6. Red needle spots, very small size. 



7. Yellow island spots. 



8. Red island spots. 



Table I. --Average 



number of 



yellow needle 

 per seedling 



spots on one 

 within full- 



lineal meter of needle 

 -sib crosses 



tissue 









Pollen 



parent 







Seed parent 



58 



19 



17 





22 



X 



57 



3 



5 



7 





12 



7 



227 



2 



7 



6 





14 



7 



382 



11 



8 



8 





8 



9 



355 



4 



11 



19 





13 



12 



121 



8 



10 



11 





20 



13 



232 



4 



15 



12 





19 



13 



230 



12 



15 



7 





18 



13 



95 



11 



12 



16 





11 



13 



179 



6 



15 



13 





19 



13 



33 



14 



14 



18 





22 



17 



X 



6 



11 



12 





16 



12 



Because resistance and suceptibility of seedlings and families to these various 

 "races" affects the number of needle spots that develop on a seedling, spot tallies 

 must include a description of the spot type. 



Tentative segregation data indicate that there is a typical gene-for-gene 

 relationship between the host and the red-normal, yellow-normal, and island-type 

 spots. Resistance in western white pine to red appears to be controlled by a dominant 

 gene, to yellow by a recessive gene, and for the island charactersitic by a dominant 

 gene. 



The fungus then grows down the needle and the next resistance reaction observed 

 is the shedding of infected needles (McDonald and Hoff 1970). This reaction begins 

 at about 9 months after inoculation and is complete at about 12 months after inoculation. 

 Genetic control appears to be due to a recessive gene (McDonald and Hoff 1971). 



A rust-resistance reaction is apparent in seedlings that keep their infected 

 needles but never develop stem symptoms. This reaction appears to be initiated at 

 the junction of the short shoot and needle fascicles when the fungus reaches the 

 short shoot (Hoff and McDonald 1971). Genetic control of this reaction also appears 

 to be by a recessive gene (McDonald and Hoff 1971). 



3 



