Regarding urediospore inoculation success, the cool chamber was best regardless of tempera- 

 ture of parent culture's chamber (tables 3 and 4). 



Table 5 . --Percent of Cronartium ribicola urediospcre inoculations that produced 



infection in 21 days. Urediospores obtained from a population of single 

 aeciospore cultures grown on Ribes hudsonianum var. petiolare INT Clone-1 

 leaf disks in a 70 F+_2 (21 C+1) chamber and inoculated back to INT Clone-1 

 in 55°F+2 (13° C+1) and 70°F+2 (21° C+1) chambers with all chambers at 16 hr days 



Infections 



Treatment Yes No Total Percent 



Aeciospore Urediospore 

 cu lture to subculture 



Warm to cool 25 16 41 . 61 



Warm to warm 14 25 ' 39 36 



39 41 ' ' 80 49 



P of a larger = 0. 025 



Total 



2 = 5.01 



X 

 d. f 



Table 4. --Percent of Cronartium ribicola urediospore inoculations that produced 



infections in 21 days. Urediospores obtained from a population of single 

 aeciospore cultures grown on Ribes hudsonianum var. petiolare INT Clone-1 

 leaf disks in a 55 F+2 (13 C+1) growth chamber and inoculated back to INT 

 Clone-1 in 55°F+2 (13°C+1) and 70°F+2 (21°C+1) chambers with all chambers 

 at 16 hr days 



Infections 



Treatment Yes No Total Percent 



Aeciospore Urediospore 

 culture to subculture 



Cool to cool 54 2 56 96 



Cool to warm 30 23 53 57 



84 25 109 77 



P of larger = 0.0005 



Total 



X^ = 24.41 

 d.f. = 1 



4 



