J. GREMMEN 



reaction of these rust provenances on eastern white pine itself, a work 

 not so easy to accomplish. 



Since C. ribicola is a native fungus of Eurasia, possibly originally 

 inhibiting Pinus oerribra L., it would not be surprising at all that only 

 a restricted number of strains of the fungus entered North America. If 

 so, newly developed resistant trees on the American continent might after 

 wards prove to be susceptible to other strains of the pathogen still 

 existing in Eurasia. However, there seems to be disagreement about 

 whether P. cembra of the Alps is the original host , and the Alps the 

 gene-center for C. ribicola (Spaulding, 1929). Other species, notably 

 P. sibivioa Du Tour, P. griffithii, P. armandii Franch., and P. koraiensis 

 Sieb. § Zucc. are also highly resistant, and their ranges are also 

 likely gene-centers (see Bingham, first of two papers in these proceedings) 



For this reason further work on this theme should be encouraged 

 under European and Asiatic conditions; in fact such work appears to be 

 an absolute necessity in order to make progress in this field. The 

 foundation of two or more disease gardens is needed. Here various rust 

 provenances and resistant host plants that have been only tested locally 

 can be brought together and studied in detail. 



Since these aspects can only be solved by more intensive interna- 

 tional cooperation, these problems will be faced in the new Subcommittee 

 on "International Resistance Test Facilities" forming part of the IUFRO 

 Blister Rust Committee of the Working Group on Genetic Resistance to 

 Forest Diseases and Insects. The target of this Subcommittee is to con- 

 tribute to a further solution of these details in the blister rust resis- 

 tance problem. If the rust race problem can be probed, and solved with 

 the help of such test facilities, then utility of resistant varieties of 

 North American white pines will be greatly enhanced there, and new per- 

 spectives will be opened for replanting these valuable species in Europe 

 and Asia. 



LITERATURE CITED 



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seedlings with the blister rust fungus. Can. J. Bot . 40: 335-337. 

 Eriksson, J. 1896. Einige Beobachtungen Uber den stammbewohnenden 



Kiefernblasenrost , seine Natur und Erscheinungsweise . Centralb. f. 



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