.ARTIFICIAL INOCULATION OF LARGE NUMBERS OF 



VIRUS MONTICOLA SEEDLINGS KITH 



CRONARTIUM RIBICOLA 



R. T. Bingham 

 Intermountain Forest and Eange Experiment Station, 

 Forest Service, U.S. Department of Agriculture, 

 Mosoolj, Idaho, U.S.A. 



.ABSTRACT 



Methods used at the author's laboratory in northern Idaho for 

 simultaneous, artificial inoculation of up to 75,000 young ?. 

 montieola seedlings in blister rust resistance, progeny test 

 nursery beds were described and illustrated. Problems of 

 securing heavy and uniform inoculation were discussed. We 

 have obtained heavy but spotty inoculation, and thus lack 

 of uniformity continues to be a costly problem. 



Delayed germination common in P. montieola seedbeds resulted 

 in 1- and 2-year-old seedlings in most row-plots. In tests 

 conducted during two successive years all seedlings in each 

 test were inoculated simultaneously in a single 72-hour period, 

 when seedlings that had germinated the first growing season 

 were 2 years old. The seedlings were examined for foliar 

 lesions approximately 1 year after inoculation and for bark 

 lesions approximately 2 years after inoculation. Compared with 

 the 2-year-old seedlings, within 85 full-sib progenies of the 

 first test, 11% more of the 1-year-old seedlings had foliage 

 infections; 28% more had bark infections. Within 97 full-sib 

 progenies of the second test, corresponding results were 20 

 and 48%. 



INTRODUCTION 



Since 1950 the Intermountain Forest and Range Experiment Station and 

 the Northern Region--both of the Forest Service, U. S. Department of 

 Agriculture--have been cooperating in a program of research and develop- 

 ment toward mass -production of western white pines [Finus montieola Dougl.) 

 that are resistant to blister rust (Cronartiion ribicola J. C. Fisch. ex 

 Rabenh.). This work necessitated an increased capacity of inoculation 

 chambers from that required for inoculating a few thousand seedlings in 

 portable flats up to that sufficient for simultaneous inoculation of more 

 than 75,000 seedlings planted in 800 running feet of 4-foot -wide nursery 

 beds (almost 1/8 acre) (Fig. 1). Meanwhile, with greater or lesser 

 success, we have attempted to increase intensity of resulting infection 

 and control the uniformity of inoculation. 



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