Hoff, R. J. 1990. Susceptibility of ponderosa pine to western gall rust within the middle 

 Columbia River system. Res. Pap. INT-416. Ogden. UT: U.S. Department of Agriculture, 

 Forest Service, Intermountain Research Station. 7 p. 



Differences in susceptibility among provenances of ponderosa pine were observed in 

 response to artificial inoculation by western gall rust. The northern inland populations 

 were highly resistant. Only 28 percent of the seedlings had galls 39 months after inocula- 

 tion. Three major resistant reactions were observed: no symptoms, visible bark reactions, 

 and fungus causing an initial infection but subsequently dying. Relationships were de- 

 tected between infection level and elevation and geographic area. Most of the variation 

 among provenances appeared to be random. 



KEYWORDS: rust resistance, disease resistance, provenance test, artificial inoculation 



