INOCULATION METHODS AND PROBLEMS IN TESTING EASTERN WHITE PINE 

 FOR RESISTANCE TO CRONARTIUM RIB I COLA 1 



Robert F. Patton 



Department of Plant Pathology , University of Wisconsin, 

 Madison _, Wisconsin, U.S.A. 



ABSTRACT 



Essentially the methodology used in testing eastern white pine for 

 resistance to Cronartium ribioola is relatively simple, but the 

 major problem remains of obtaining severe and uniform infection. 

 Natural inoculation may be incorporated in progeny testing 

 programs, but little control can be exerted over this except for 

 site choice and preparation and the possible increase of inoculum 

 in the area. Artificial inoculation methods are classed as spore 

 casts, spore suspensions, and infected-tissue grafts. Spore cast 

 methods have been successful, but lack the refinement of standardi- 

 zation or control over amount of inoculum applied. 



An adequate supply of inoculum is essential, and this has been 

 guaranteed to a limited extent by the development of ribes 

 gardens of leaf-retaining strains of Ribes nigrum. So far 

 dependence has been entirely on freshly-collected inoculum, and 

 reliable methods of storage of telia or of basidiospores have 

 not been developed. 



Emphasis is given to the fact that each stage of development in 

 the series of activities encompassed by inoculation requires 

 different environmental conditions. These various external 

 influences may affect the efficiency and reliability of inocu- 

 lation. Age of stock is one factor that is under the breeder's 

 control. Also, fluctuating temperatures within the range of 

 about 4 to 21°C are known to favor infection through stimulation 

 of infection structure formation. 



The major problems at present relate to lack of standardization 

 of inoculum and the inability to relate quantitatively host 

 response to amount of inoculum. Improvement in present 

 methodology may come from a better understanding of factors 

 influencing the infection process and from development of better 

 methods of applying inoculum. 



* Published with the approval of the Director 3 Wisconsin Agricultural 

 Experiment Station. Experience and results of the author reported here 

 have come from investigations supported in part by the Wisconsin Department 

 of Natural Resources (formerly Wisconsin Conservation Department) 3 National 

 Science Foundation Grant GB-3297 , and U. S. Forest Service Grant No. 1 

 (4000). 



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