BASIC BIOLOGY OF RUSTS AND RUST DISEASE RESISTANCE: 

 >DDERATOR'S S1M1ARY 



CO. Person 

 Department of Botany , University of British 

 Columbia, Vancouver, B. C. 3 Canada 



Each of today's speakers has covered a large area of basic biology. 

 To attempt a summary of all that has been said would be a formidable task. 

 Since I consider myself not qualified to make the attempt I have chosen, 

 instead, to comment on a few points that were of special interest to me. 



One point which has been emphasized several times today is that the 

 problem of breeding for resistance to white pine blister rust is likely 

 to be quite different from that of breeding for rust resistance in agri- 

 cultural crops. A collection of these differences, taking wheat and stem 

 rust as an example from agriculture, would certainly include the following: 



White Pine Wheat 



Generation time: years 3 to 4 months is usual 



Mating by cross-fertilization by self-fertilization 



Populations genetically diverse homogeneous 



Host genetically diploid polyploid 



Infecting rust haploid diploid (dikaryotic) 



Alternate host present generally absent 



There are probably other ways in which the two situations differ sharply. 

 It seems worthwhile, therefore, to re-emphasize the point made by previous 

 speakers, that breeding procedures which are known to be successful in 

 agriculture need not be successful in forestry. 



Because large acreages are often sown to a relatively small number of 

 "pure" cultivars it is not usual in agriculture to approach disease 

 problems from the point of view of populational or ecological genetics. 

 One result of this is that we actually know very little about the genetics 

 of non-agricultural, or naturally occurring, parasitic systems. Since 

 the kind of disease epidemic that is familiar to agriculture is not charac- 

 teristic of undisturbed, natural populations it seems evident (to me at 

 least) that regulating mechanisms are present in natural systems which 

 operate in such a way as to keep host and parasitic populations in balance 

 with each other. 1 Knowledge of such regulatory mechanisms (if they exist) 

 would provide the basis for new approaches to the solution of disease 

 problems in agriculture as well as in forestry. Since I believe that 

 such mechanisms do exist, I view the white pine blister rust problem as an 

 opportunity to discover new principles in the biology of disease. 



1 Q. 



See paper by Hoff and McDonald, these proceedings. 



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