PATHOGENIC VARIABILITY WITHIN FUSIFORM AND EASTERN GALL RUST 509 



Comparisons between these infection data with C. quercuum and those 

 of Hedgcock and Siggers with the same organism are difficult to make 

 because Hedgcock and Siggers did not always indicate the original host 

 source of the collections. There are also differences in inoculation 

 techniques. The majority of Hedgcock and Siggers inoculations were made 

 by inserting telia into slits in the phloem of young shoots. It is not 

 known just what effect this radical method of inoculation might have on 

 a species with borderline resistance. 



The differences between the two collections of C. quevouvm demon- 

 strated by our data (Table 2) are supported by similar findings reported 

 by Kais and Snow in these proceedings. Therefore, it can be said that 

 distinct pathogenic races, using the term in the classic sense, exist 

 within the overall population of C. quercuum. 



It is possible that C. fusiforme may be less variable in patho- 

 genicity than C. quercuum. C. quercuum has a much wider natural range, 

 covering most of the eastern half of the country and it is common on a 

 relatively wide range of pine hosts in the North and South. C. fusiforme 

 is found in a much more limited geographic area in the South, and has 

 only two primary hosts, loblolly and slash pine. Therefore, it would be 

 expected that the chances for the development of pathogenic differences 

 would be much greater in the case of C. quercuum, although the possibility 

 of such variability should not be ruled out for C. fusiforme. 



LITERATURE CITED 



Anderson, Neil A. 1963. Eastern gall rust. U.S. Dep . Agr. Forest Pest 



Leaflet 80. 4 p. 

 Campbell, W. A., Sanford P. Darby and John C. Barber. 1962. Fusiform 



rust, an obstacle to the establishment of grafted slash and loblolly 



pine seed orchards. Georgia Forest Res. Council Paper 11. 5 p. 

 Hedgcock, George G., and Paul V. Siggers. 1949. A comparison of the 



pine-oak rusts. U. S. Dep. Agr. Tech. Bull. 978. 30 p. 

 Verrall, A. F. 1958. Fusiform rust of southern pines. U. S. Dep. Agr. 



Forest Pest Leaflet 26. 4 p. 



FLOOR DISCUSSION 



(Discussion here also covers the previous paper by Kais and Snow.) 



POPE: Dr. Powers, do you think that what we are calling races here 

 in the pines is the same as what people working with stem rusts of wheat 

 are calling races, in light of the fact that here we are using a number 

 of pine species whereas with the wheat rust, they are talking about 

 varieties? 



POWERS: Of course, there are some differences, but as I mentioned, 

 they do have five different species involved in their standard wheat 

 stem rust differentials. Within the standard differentials you have 

 Triticum vulgare and a group of other wheat species, so essentially they 

 are trying to determine differences between their different physiologic 

 races with different host species just as we have the different pine 

 species. There is another point to be mentioned here and that is that 

 we do not have anything comparable to their situation going from a zero 

 fleck all the way up to a four infection type. We are simply talking 



