BREEDING RUST RESISTANT POPLARS 429 



Taris, B. 1968. Rusts of poplar observed in France. Ann. Epipht. 19(1) 



5-54. 

 Toole, E. R. 1967. Mel amps ora medusae causes cottonwood rust in Lower 



Mississippi valley. Phytopathology 57: 1361-1362. 

 Veldeman, R. 1964. Le rouille du peuplier, p. 1-14. In FAO/CIP Congres 



centre europeen. 

 Vloten, H. van. 1944. Is verrijking van de mycoflore mogelijk? (Naar 



aanleiding van de populierenroest) . Tiidschrift, PI. Ziekter 50: 49-62. 

 Ziller, W. G. 1965. Studies of western tree rusts. VI. The aecial 



host ranges of Melampsora albertensis > M. medusae 3 and M. occidentalis. 



Can. J. Bot. 43: 217-230. 



FLOOR DISCUSSION 



(Also covering preceding paper by Allan Klingstro*m) 



ZUFA: I have two questions. Dr. Klingstrom, is the heritability of 

 the resistance against Melampsora pinitorqua known? Dr. Steenackers , does 

 the resistance of the same clones change in different environments or if 

 confronted with different species or races of rust? 



KLINGSTROM: Not very much is known about the inheritance of resis- 

 tance to Melampsora pinitorqua. The only thing I can say is that a dif- 

 ference seems to exist between clones and progenies. The inheritance 

 from parent clones to progenies has not been studied very much. 



STEENACKERS: Well, in the first place we have tried to select clones 

 that were completely free of rust. And then we tried to plant these 

 clones on different sites in Belgium and at different latitudes, for 

 instance, 45° latitude in the southern part of France, 51° and 52° lati- 

 tude in Belgium. The clones that were completely free of rust, in our 

 nursery in the beginning, still are completely free of rust at the various 

 sites. Now I believe that most of the rust species are likely to be 

 represented everywhere in western Europe because the host plants are 

 present throughout western Europe. For the past 5-6 years we have been 

 testing clones that are more or less susceptible. These susceptible 

 clones score one or two, we have planted these clones at two latitudes. 

 And after 5 years the susceptibility of the clones remained the same, but 

 there is a difference in the degree of attack. The clones are less 

 infected at 45° latitude in southeast France and more infected at 51° 

 latitude in Belgium. Some of the clones have been observed for 15 years 

 and still there is no change in susceptibility. 



SCHREINER: I would just like to point out that the specific name 

 Melampsora medusae has no real meaning any more for the U.S., and I doubt 

 very much whether we have any area where we have a single species. I know 

 in the northeast we have at least four. This is based on observations 

 over many years of the alternate host. I have come to the point where I 

 no longer use the specific name medusae. I simply say Melampsora spp. I 

 did want to point out that there are many species and perhaps many more 

 than you have in your own country. 



STEENACKERS: I thank you very much, Dr. Schreiner, for this informa- 

 tion and I hope these species will never come to Europe. 



