310 K. STERN 



resistance. Perhaps host-parasite equilibrium is possible only if the 

 degree of general resistance is high. Why not try it with species hybrids? 

 Of course this would be experimental, but we're only sure after having 

 performed the experiments. 



SCHREINER: As I listen here I wonder whether we aren't making a 

 case for a collection of germ plasm to provide the greatest possible 

 amount of panmixis. In order to develop populations in which we can 

 define this cryptic variability we will have to break up gene associa- 

 tions. Perhaps this is what Wright was referring to when he wrote his 

 paper on preadaptation many years ago. I wonder whether our wheat- 

 breeder friend Dr. Pope would agree that what we need is perhaps a breaking 

 up of some of these gene associations. Are we, perhaps, making a mistake 

 in assuming that we have a very widely heterozygous population in any 

 one stand? 



POPE: It's really the same speech over again. Had. Dr. Borlaug 

 commented first there would have been nothing for me to say. He has 

 really done what I was suggesting on a world-wide scale. You can read 

 the plants just like you can read the page of a book. The phenotype of 

 the individual, resistant natural-stand trees tells only part of the 

 story. Bingham's seedling progeny tests tell another part of the story. 

 The progeny, mature-tree testing yet to come will be another part of that 

 story. The only thing I can suggest is that you put your plants together 

 as best you know how, then because we don't know very much about resistance, 

 put them together in many other ways not suggested by what you know now. 

 I would include the wildest possible crossing in logical and illogical 

 ways. The most important findings I have made in wheat have usually been 

 accidents, something I happened to see alongside the plots where I was 

 hard at work. Not much I did on purpose really worked very well. You 

 must put your trees together in a way so that all these "accidents" can 

 happen. These accidental findings will be more meaningful than many of 

 the experiments you plan carefully. But this course of action requires 

 large numbers of parents and larger progenies than now being used. 



BINGHAM: In defense of us foresters I would point out that we are 

 necessarily far, far behind crop breeders in gaining--even what the crop- 

 breeder might consider to be background information--on our tree rust 

 resistance systems. First, we began intensive breeding work only about 

 20 years ago. Second, we face relatively lengthy tree reproductive 

 cycles (with most pines it's 3 years from pollination to 1-year-old seed- 

 lings) and even longer resistance testing cycles (3 to 4 years from 

 inoculation to appearance of foliar and early bark resistance reactions) . 

 Thus I feel that we first need to gain for tree rusts some of the funda- 

 mental knowledge the crop breeder already has and accepts, however 

 unconsciously, as a prelude to his work. I think we must find and be 

 able to recognize specific resistance reactions and vertical resistance 

 genes. This knowledge will help us to do, Dr. Pope, what you may be 

 doing intuitively—recognizing effects of vertical genes and possibly 

 eliminating the ones that you know from experience just don't work here. 

 At present the forester can't do this, even consciously, so I feel we 

 must strive to gain basic information about single resistance genes and 

 their reactions. 



