STEM RUSTS OF CONIFERS AND THE BALANCE OF NATURE 533 



THE "KNOWLEDGE GAP" 



In 1962 it was estimated that 10,000 questions had to be answered 

 before a man could be landed on the moon and returned to earth. This 

 venture, of course, was successful. However, many scientists involved 

 with space exploration did not feel that they were ready to place a man 

 on the moon. They thought the risk factor was still too high. In other 

 words, not all the questions were answered. 



A similar philosophy would be useful for producing a new population 

 of blister rust -resist ant western white pine. One would prepare a list 

 of questions. Then at certain intervals he would tally the questions 

 answered while adding new questions that may have arisen. Consequently, 

 once enough information is accumulated to estimate the risk of failure 

 the decision can be made to go ahead with the production of this new 

 population. 



The following list of general questions reflects our lack of know- 

 ledge. Each breeding program should establish a detailed list of questions 

 for its specific host-parasite system. 



1. Do the Eurasian pines -Cronavtivm ribicola systems represent a 

 "balanced symbiotic" condition? 



2. Does the "balanced symbiotic" condition for both the hard and 

 soft pines reflect a common evolutionary history resulting in a common 

 set of factors for resistance? 



3. Where is the gene center of white pine blister rust? 



4. What are the sites, mechanisms, and inheritance of the factors 

 for resistance in each pine host-stem rust system? 



5. What is the variation in aggressiveness, virulence, and other 

 characters of the rust organism in each pine host-stem rust system? 



6. What are the frequencies of each identifiable gene in each com- 

 plete pine host -stem rust system? 



7. What are the effects of epidemiological factors on the 

 establishment and maintenance of "balanced symbiosis"? 



8. Is there a genetic relationship between resistance genes and 

 genes controlling other fitness and quality characters? 



9. What are the mechanisms of genetic variation in the stem rusts? 



LITERATURE CITED 



Bakshi, B. K. , and S. Singh. 1967. Rusts on Indian forest trees. Indian 



Forest Rec. 2: 139-204. 

 Bingham, R. T. 1954. Development of rust resistant white pine, 1954, 



4 p. In U. S. Dep. Agr. , Forest Service Region One, Blister Rust 



Control Annu. Rep. n.p. (Mimeo) . 



