INOCULATION OF EASTERN WHITE PINE WITH BLISTER RUST 383 



Loegering, W. Q. , D. L. Harmon, and W. A. Clark. 1966. Storage of 



urediospores of Puccinia graminis tritici in liquid nitrogen. Plant 



Dis. Rep. 50: 502-506. 

 Patton, R. F. 1961. The effect of age upon susceptibility of eastern 



white pine to infection by Cronartium ribicola. Phytopathology 51: 



429-434. 

 Patton, R. F. 1962. Inoculation with Cronartium ribicola by bark-patch 



grafting. Phytopathology 52: 1149-1153. 

 Patton, R. F. 1967. Factors in white pine blister rust resistance, p. 



876-890. In Proc. XlVth IUFRO Congress, Vol. 3. Munich, Germany. 



926 p. 

 Patton, R. F., and A. J. Riker. 1966. Lessons from nursery and field 



testing of eastern white pine selections and progenies for resistance 



to blister rust, p. 403-414. In H. D. Gerhold et at. (ed.), 



Breeding pest-resistant trees. Pergamon Press, Oxford. 505 p. 

 Riker, A. J., T. F. Kouba, W. H. Brener, and L. E. Byam. 1943. White 



pine selections tested for resistance to blister rust. J. Forest. 41: 



753-760. 

 Snell, W. H. 1942. The production of sporidia of Cronartium ribioola 



on cultivated red currants in relation to infection of white pine. 



Amer. J. Bot . 29: 506-513. 

 Snow, G. A. 1968. Basidiospore production by Cronartium fusi forme as 



affected by suboptimal temperatures and preconditioning of teliospores. 



Phytopathology 58: 1541-1546. 

 Spaulding, P., and .Annie Rathbun-Gravatt . 1925. Longevity of the telio- 

 spores and accompanying uredospores of Cronartium ribioola Fischer in 



1923. J. Agr. Res. 31: 901-916. 

 Sapulding, P., and Annie Rathbun-Gravatt. 1926. The influence of 



physical factors on the viability of sporidia of Cronartium ribicola 



Fischer. J. Agr. Res. 33: 397-433. 

 Van Arsdel, E. P. 1968. Stem and needle inoculations of eastern white 



pine with the blister rust fungus. Phytopathology 58: 512-514. 

 Van Arsdel, E. P., A. J. Riker, and R. F. Patton. 1956. The effects of 



temperature and moisture on the spread of white pine blister rust. 



Phytopathology 46: 307-318. 



FLOOR DISCUSSION 



(Discussion here also covers the previous paper by R. T. Bingham.) 



MCDONALD: Dr. Patton, your reports on the influence of seedling age 

 on susceptibility have brought a question to my mind. How do you know 

 the effect is not one of genotype? If you are comparing the younger tree 

 of one genotype with the older tree of another it seems to me you can't 

 eliminate this possibility. 



PATTON: Although I didn't have time to go into it, I have made 

 tests on the same full-sib progenies at different ages and have obtained the 

 same results. Also, I have inoculated grafts of the same tree at different 

 ages and results have indicated the same sort of age effect. We haven't 

 done much with inoculating a single tree, say at ages 1 and 10 years, but 

 in large-scale progeny tests we found definitely that susceptibility 

 decreases with age. 



MCDONALD: Well, I agree with the difference between 1- and 2-year- 

 old seedlings. 



