506 



H. R. POWERS, JR. 



Mexico and eastward to the Atlantic coast (Anderson, 1963) . In contrast 

 to fusiform rust, this fungus causes globose or cerebroid galls on its 

 pine hosts. It also differs from fusiform rust in that it causes only 

 slight damage to the southern pines that it infects, such as shortleaf, 

 sand (P. Clausa (Chapm.) Vasey) , and Virginia (P. virginiana Mill.). 

 However, these two rust fungi are nearly indistinguishable on their oak 

 alternate hosts. 



Although there is information about the pine host ranges of these 

 two fungi (Hedgcock and Siggers, 1949), very little is known about the 

 pathogenic variability inherent within each population. The objective 

 of this study was, therefore, to evaluate the variability of several 

 collections of both these fungi as expressed by infection on a range of 

 hard pine species. 



Four aeciospore collections of C. fusiforme from three geographic 

 areas of the South and two aeciospore collections of C. querouum 3 one 

 from the Southeast and one from the North Central states, were used 

 (Table 1). Each rust collection was made from a single gall. Inocula- 

 tion with one rust collection was completed before work with the next 

 rust began, in order to prevent contamination. The aeciospores were 

 used to inoculate northern red oaks {Quercus rubra L.). Telia that 

 formed on the oak leaves were suspended for 48 hours over 4- to 6-week-old 

 pine seedlings in a mist chamber at approximately 70°F. Sixteen species 

 of hard pine, including both native and exotic species, were inoculated. 

 Between 300 and 400 seedlings of each species were inoculated with each 

 rust collection. The inoculated seedlings were grown for 7 to 9 months 

 in a greenhouse and then were examined for stem galls. 



Table 

 study 



1. 



Collections o 



f rust used in pathogenic variability 



j 



Culture 

 number 



Sp 



ecies 



Geographic source 



Pine host 





631 



C. 



fusiforme 



Upper Piedmont South 

 Carolina 



loblolly 





632 



C. 



fusiforme 



Upper Piedmont South 

 Carolina 



loblolly 





645 



c. 



fusiforme 



Lower Coastal Plain 

 South Carolina 



loblolly 



i 



WSP1 



c. 



fusiforme 



Mississippi (albino 

 strain) 



slash 





648 



c. 



querouum 



Western North Carolina 



Virginia 



< 



671 



c. 



quercuum 



Minnesota 



jack 



9 



